Renewable Energy 8 – Compressed Air

Like Hydrogen fuel, compressed air is not a direct renewable fuel but a secondary fuel option, derived as an energy storage technology.  Compressed air has been used for well over a century to drive equipment – think compressed air guns in the building industry.  Compressed air energy storage (CAES) uses electricity to compress air that be used to drive a turbine generator to produce electricity on demand (when needed), or even to drive a pneumatic engine as a transport fuel.      

Electricity and Storage

CAES has been used for many decades with the compressed air either produced via a pump on-site or stored in high pressure cylinders.  More recently, underground caverns (e.g. solution-mined caverns in a salt deposit) are being considered because of their exceptionally large storage capacity. The cavern can be insulated and compressed air stored with little temperature change and heat loss. The low cost of construction for these compressed gas storage systems is an advantage, using the cave walls to help contain the pressure. 

As with all energy sources, CAES is only as cleanly renewable as the fuel used to initially create the energy.  Providing that the energy used to compress the air is from a renewable source such as wind or solar, then it is a clean source.  In the past, fossil fuels sources were often used to compress the air, which both maintains the pollution problems of fossil fuels and greatly diminishes the efficiency of even using compressed air as an alternate energy storage.  The lifetime of these storage systems is expected to be well over a century, which makes their investment a good option to consider.   

The big difference between storing compressed into high pressure storage tanks on the surface or compressing it into caverns is a crucial one.  Air compressed on the surface is simply stored directly in to the storage container.  Compressing air for storage underground requires a multi stage pumping and retrieval system – it isn’t just a large-scale version of a compressed air tank.  This means energy is used to manage the cavern storage systems thereby greatly reducing the efficiency of the system.  Its advantage comes when large amounts of renewable electricity are being produced that can be used to compress the air for larger scale on-demand turbine electrical generation, otherwise the electricity would simply be discharged in to the atmosphere. 

Transport options

A compressed-air vehicle (CAV) is simply a vehicle with a pressurized tank of air as the fuel supply.  The pressure of the air expands to drive a Pneumatic motor.  These kinds of motors have been in use for many decades and have applications in torpedoes, vehicles used in digging tunnels, and early prototype submarines.  More recently, research has been on passenger cars.  The main problem has been the need to show CAES competiveness with other options such as hydrogen fuel.  Air compressed using renewable energy sources is completely non-polluting in both its production and in use as a fuel – nothing is burned, it is just air compressing and expanding.  The only danger from CAES is being too close to a direct rupture of a storage tank, which is quite a minimal risk when compared to other forms of energy storage.  Gasoline and Diesel, the transport fuels we currently accept and use every day, are extremely risky when it comes to potential hazards.  Economists have analyzed the cost benefits of using compressed air in various CAES transport systems.  Some vehicles could have on-board compressor units plugged into the electrical mains (assumes renewable electricity sourced) while others could refill at large compressed air service stations. The cost ranges from less than $1 to $1.25 per each 50 mile driven depending on the storage source.  This makes it comparable to modern transport costs. 

There are several prototype vehicles out there.  The range of the cars or larger transports (trucks, buses, etc…) is only limited by the size of the storage tanks.   The top speed of most current prototypes run only on compressed air is about 50 mph.  This makes them currently ideal for urban use (especially with the zero emissions) but more marginal for long distance travel where time is of the essence.  Tata Motors India was a pioneer with the use of the CAES transport in 2007 and now has a small lightweight model produced with (Motor Development International France) called the ‘Airpod’ that gets about 50 mph top speed with a range of 160 miles.    

There are currently several CAES-hydrid vehicles operating efficiently while research continues on using CAES as a main transport fuel.  According to a recent interview of Loveland, Colorado’s, truck fleet, the fleet manager Steve Kibler, says, that hybrid hydraulic drive system called ‘RunWise’ uses a technique that stores braking energy and hydraulic fluid and then releases it to accelerate the truck up to 35 miles per hour, with less reliance on the engine, Kibler said, “With very little operator training, we were able to achieve 48 percent fuel savings, and a Return on Investment of 6 years on hydrid trash trucks compared to regular diesel trash trucks.

Renewable Energy 7 – Hydrogen fuel and fuel cells.

Often touted as a renewable fuel option, but it is not a direct renewable fuel but a secondary fuel option.  This means that it requires energy to break the bonds of another chemical become useful as a fuel.  The great thing about hydrogen is that burning it as a fuel is almost pollution free – the main waste being oxidized hydrogen – water!  With only minor modification, a standard engine can burn injected hydrogen fuel.  If used in a fuel cell it is completely pollution free, except as I have said several times already within this blog, for the construction of the fuel cell. 

Hydrogen Fuel – While hydrogen is one of the most abundant atoms in the universe, its down side is that it is almost always attached to other atoms e.g. Water (H2O) and methane (CH4) being the two most common sources used.  Deriving hydrogen from methane does little to alleviate the pollution problems associated with fossil fuels, but deriving hydrogen from water can be a renewable source.  Think about it for a second.  You pass a small electrical charge (electrolysis) into pure water and you get hydrogen gas and oxygen, and when you burn the hydrogen (oxidize it) you get water back again with the added bonus of the energy of the oxidation.  Essentially the whole process is non-polluting, depending of course where the energy for electrolysis is derived. The kicker here is that obtaining hydrogen takes energy so at best it is a zero-sum gain.  What makes it valuable though is the fact that hydrogen is a storable energy form that can be used in several ways to produce electricity or to power transportation.  When renewable energy generation sources are used (e.g. wind, solar) and demand is down, the extra energy generated can be used in electrolysis to form hydrogen stores.  (Scroll down for more about storage options)       

Hydrogen Fuel Cell – in its simplest form, a fuel cell is where the hydrogen atom is stripped of its two electrons (anode) and the hydrogen ion allowed to pass through a proton exchange membrane (only conducts positively charged ions).  The two electrons then must flow through a wire to the other side of the membrane to rejoin the hydrogen ion at the cathode, which then oxidizes to form water as the waste.  (Electricity as we use it is simply the movement of electrons in a wire).    

Hydrogen Flammability and storage – When talking about storing hydrogen fuel, skeptics always point to the 1937 disaster of the Hindenburg dirigible.  It is true that hydrogen is a highly reactive gas (oxidizes readily) and compressed hydrogen gas is so reactive it becomes explosive in its speed of oxidation.  Even if compressing hydrogen were the only option of storage (it isn’t – see below), it is still a better option than liquid petroleum fuels.  For instance, a gas tank is ruptured, the liquid flows down to the ground from the tank and the fumes above the liquid can ignite to create an explosive result (note how Hollywood loves to show this is car chases with cars exploding).  Many of the Hindenburg survivors were below the dirigible when it caught fire, because hydrogen is lighter than air (the reason it was used to lift the dirigible) and all the fire went straight upwards from the point of ignition.  Another minor drawback of hydrogen is that volume for volume with energy efficiency it needs more space than say, gasoline.  So, a hydrogen fuel tank would take up four times the size of a fuel tank than a gasoline tank for the same distance to be travelled.  This, however, is a minor nuisance considering that there are at least six ways to store hydrogen, except for high pressure tank storage, that are safe from catastrophic explosion problems

The hydrogen gas can be stored in high-pressure cylinders up to 800 bar (11, 500 psi), however, with more energy use can be used to store liquid hydrogen (safe from explosion) in cryogenic tanks, yet this requires insulated tanks of course.  Hydrogen gas can be adsorbed onto nano-porous materials with a large specific surface area.  The advantage here is that the gas is at atmospheric (ambient) pressure and therefore the gas is non-flammable until released form the adsorbed surface at a slow rate.  Depending on the material used, it may be necessary for the storage containers to be under some elevated pressure (up to 1500 psi, yet still non-flammable).  The gas can be stored in a lattice metal matrix as a metal hydride under atmospheric pressure, again non-flammable until slowly released.  Metal hydrides because of their chemical make-up Metal hydrides because of their chemical make-up are highly effective at storing large amounts of hydrogen in a safe and compact way.  Finally hydrogen can be chemically bonded in at ambient pressure initially being adsorbed at higher pressure and released using elevated temperature, or using metals and alloys are capable of reversibly absorbing large amounts of hydrogen.   volumetric densities of hydrogen are found in metal hydrides.  The chemical bonding technology is showing valuable options in using hydrogen as a future fuel.   

The major advantages of hydrogen as a fuel are that by converting chemical potential energy directly into electrical energy, hydrogen fuel cells avoid the “thermal bottleneck” (a consequence of the 2nd law of thermodynamics).  This makes the generation of hydrogen from renewable energy environmentally friendly.  Fuel cells have few drawbacks and are very efficient, have no moving parts to wear out and produce no pollution. 

Iceland transport Infrastructure – To show the possibilities of using hydrogen as a viable transportation fuel, Shell energy company is helping Iceland move to renewable energy.  With its abundance of geothermal and hydroelectric power, Iceland is leading the way to demonstrating how hydrogen fuel can be used for both storage and especially transport.  The Icelandic bus fleets now use hydrogen fuel cells and the government is ramping up the system to fuel all Icelandic cars with hydrogen fuel.  All locals will be able to go to a regular gas station and fill up on hydrogen like they would with regular gasoline.  Economist insist that moving to a hydrogen fuel economy is too expensive, but Iceland is bucking this fallacy and is fast becoming the model for how renewable energy can exist in highly developed countries.    

Renewable Energy 6 – Biomass energy systems

Burning wood is probably one of the oldest and most common forms of producing heat and energy.  Yet, as anyone who has ever sat around a campfire will attest, the smoke can be problematic.  Photosynthesis is one of the most incredible mechanisms in nature – diffuse light energy from the sun is captured and turned into concentrated chemical energy – the most common of which is cellulose.  Yet, the release of that heat and light causes the release of the chemical materials (carbon dioxide and ash – residues of all the other chemicals) in to the atmosphere.  Of course, some heavier ash is left at the site if combustion.  The obvious problem is that all biomass energy is a reverse of photosynthesis, yet that being said, it still has a lot of potential to power our systems and is completely renewable.  

There are basically four types of biomass in use today – Wood and agricultural products that accounts for about 44% of current biomass usage.  

  • Wood and biowaste from burning dead trees, and waste wood from places like wood mils, forest debris, building demolition sites, and even dried animal manure.  Many people in more affluent areas often have open wood fires that are both esthetically pleasant and can make use of dead wood.  In rural areas the pollution is not severe but in a large town or city would quickly come to produce the smoke smogs that were so devastating to health in the 1700s and 1800s.   Waste wood can be burned directly or it can be processed into smaller pellets for incineration in higher temperature boiler systems.  This is a way to ‘reuse’ wood products, but in the end it is simply an advantageous economic aspect of energy generation and does little to alleviate pollution problems. 
  • Alcohol fuels (like Ethanol or Biodiesel), that are derived from crops like corn and algae.  One of the big problems with using crops is that these are also our food supplies. It’s a strange choice – food or fuel.  In the USA we have a surplus of food, but many developing countries struggle to feed their people let alone think about using what food they do produce for fuel.  Add to the problem of developed countries financing fuel crop growing in these developing countries creates hunger problems for people.  Add to this the problem that growing these crops is also energy intensive technology.  Alcohol is a lot cleaner to burn than fossil fuels – although there is still some pollution – but when the total spreadsheet is framed for Alcohol fuels, the only real option worth considering is that of algal alcohol, but that is still in its infancy.   There is E85 fuel available but a main problem of alcohol fuels is that alcohol can be corrosive to components of an engines fuel injection system thereby requiring more stainless steel and erosion resistant components be added to the engine. 
  • Solid waste incineration (conglomerate biomass – waste to energy or energy from waste)has been around for a few decades.  At first it was a solution to the growing solid waste problem in that it burned trash in traditional coal burning electrical generation plants.  The problems with burning solid waste is that the mixture of materials includes plastics and a multitude of other chemically derived products.   If the waste is not burned at a high enough temperature the resulting emissions can form toxic byproducts that need further treatment making this a potential health and economic problem.  Strict regulations are required to ensure public health safety and sorting trash before it is burned can be a costly process.  One advantage of this is that the emissions tend to be carbon dioxide, which is less polluting than Methane emissions often found from simple biological degradation with a trash dump – the old now rapidly disappearing form of trash disposal in the developed world but still prevalent growing problem in the developing world. 
  • Landfill gas and biogas.  This energy option derived from the methane produced by biodegrading trash or biodegrading wet animal manure.   Most landfills today are aseptic in that degradation is limited because of the compartmentalized nature of how trash is now stored in landfills.  The trash is packed into the landfill and then surrounded by clay.  This restricts the oxidation biodegradation thus keeping the trash in its undigested form for long periods.  What degradation does occur is anaerobic and produces methane.  In order to safeguard the landfill from potential explosive ignition of methane pockets, methane pipes are added to the landfill to vent off the methane.  Rather than vent the methane, many landfills are now capturing the methane for energy generation.  This works for the developing world and big cities around the world because of the immense amounts of trash generated in a consumer society.  In the developing world, however, one of the biggest problems, especially in rural and remote areas is that of over use of wood fuel.  Deforestation has been almost catastrophic in this areas with locals walking many miles a day to find enough wood for cooking and heating.  These people generally tend to be more pastoral and have many animals and hence lots of wet animal manure on hand.  Relatively small Biodigestor units can be given to each family where the wet manure is kept in a sealed tank to digest anaerobically.  The resulting methane each day serves as both the cooking and heating fuel, thereby relaxing the demand for fuel wood.  This has benefitted these rural villages in economic and ecological ways as well.  The reduction of fuel wood use has allowed the depleted forest to regrow, and the time saved in not having to find fuel has given the women especially, time to devote to crafts they can sell at local markets to tourists.  The men have been reported happy with the resulting digested liquid organic sludge as it is a better fertilizer for their crops than simple manure.  Of course, this biogas from biodigestors can be scaled up to community level to produce methane for larger numbers of homes.

While biomass can be a boom for many areas, especially more rural and remote areas, it is difficult to see how it can be scaled up for industrialized systems.  While biomass is renewable it often just substitutes for a more polluting alternative.  It does have advantages in that it usually produces less pollution.  In developed countries, the use of biomass such as algae has a lot of promise to substitute for oil-based fuels without disrupting the existing infrastructure and so as a stop gap option is beneficial.  One of the big aspects of biomass is the incredible amount of non-crop cellulose to be found on the planet.  This has been a difficult problem to crack – how to use cellulose economically, because degrading plant cellulose is not easy. 

There is some recent research that could soon change that.  In a 60 minutes episode on January 6, 2019,  unlikely genius inventor Marshall Medoff talks about a new technique to break down Cellulose cheaply and economically viable.  As Marshall says about his work, “What I thought was, the reason people were failing is they were trying to overcome nature instead of working with it.”  “What MIT trained chemist Craig Masterman has done is help implement Medoff’s novel idea of using electron accelerators to break apart nature’s chokehold on the valuable sugars inside plant life – or biomass. The accelerators can break the cellulose down to simple sugars that cane be used for a myriad number of functions from fuels to foods, and the process can even break down plastics easily.  The process doesn’t disrupt existing infrastructure systems but complements them with low polluting alternatives. 

Renewable Energy 5 – Ocean and Tidal Energy Generation

Before I begin, I will freely acknowledge that this option is not really great for Colorado or anywhere else in the middle of the Continental USA without expensive electrical  transmission systems.  Having admitted that, it is useful to note that according to the National Oceanic and Atmospheric Administration (NOAA) the official shoreline of the USA is estimate to be 95,471 miles.  That is a lot of constant renewable energy waiting to be tapped.  Unlike coastal wind towers that stand above the water’s surface capturing variable wind currents, most ocean power lies out of sight (an important consideration for those people worried about esthetic vistas) below the surface – wave power may be more visible depending on the technology used.   Again, this is pollution free energy generation once the technology has been built and set in place.    There are three energy sources from oceans:

  • Tidal power: The twice-daily flow of tides (rising and falling of seas due to the moon’s constant gravitational pull) creates energy of motion that can be converted to electricity. Even on a calm day the tides roll in and out with rhythmic constancy (predictable and stable).  Current technology has three different ways to utilize tidal energy: tidal streams, barrages, and tidal lagoons. In essence, what this means is that tidal rises and falls are captured in a system that resembles hydroelectric power, but unlike terrestrial falling water hydro, the incoming and outgoing tidal energy can be utilized.  For most tidal energy generators, turbines are placed in tidal streams and since water is more dense than air, tidal energy is more powerful than wind energy for spinning underwater turbines.
  • Wave power: This is very similar in many ways to tidal power, in that the ocean energy is used to spin a turbine, but in this case the actual wave energy is usually used as an indirect motion to spin the turbine. The incoming waves can enter a chamber where the waves compress the air in the chamber, which is then forced through an opening to spin the turbine in a housing above the water level (often on the edge of the shore).  The air forced in and then pulled back by the wave power can spin the turbine with a gearing shifter that keeps the turbine spinning in the same direction whether the air is moving in or out of the chamber.  Wave energy is produced when electricity generators are placed on the surface of the ocean. The energy provided is most often used in desalination plants (an important potential for clean fresh water in coastal regions), power plants and water pumps. Energy output is determined by wave height, wave speed, wavelength, and water density.
  • Thermal power: This technology exploits differences between warm water (usually at the surface) and cold water (usually down below 15 meters). While not yet commercially developed, the potential is enormous.  The technologies under study can use warm surface water that is piped into facilities where it evaporates volatile substances (e.g., ammonia) to turn turbines.  Cold, deeper water is then used to condense the substances and start the cycle again.  Ocean Thermal Energy Conversion (OTEC) project research has been run in Hawaii and elsewhere, but there are no commercial operations yet, but The OTEC plant located in’s Hawaii’s NELHA plant (in Kailua-Kona) could become commercially operational in the near future.

Renewable Energy 4 – Geothermal Energy

This is not a new option, but it is one that receives little attention in the U.S.  Geothermal energy is simply using the thermal energy generated and stored in the Earth.  For technical reasons, there are two types of Geothermal:

1.  Volcanic based (from deeper underground) and heat stored in the ground nearer the surface (stored heat within 250 ft of the surface).

Hot magma chambers and volcanic activity that lay relatively close to the Earth’s surface can heat deep water tables creating thermal vents.  These hot thermal water vents often show at the surface as hot springs.  Throughout the western U.S. there are many hot springs attesting to the volcanic potential below the western part of the country besides the incredible volcanic crucible known as Yellowstone National Park and the Volcanoes of the Pacific North West and Alaska.  How much of the volcanic activity can be considered for energy use potential is still debatable since tapping into natural spring areas and national parks could inadvertently disrupt the systems that make those parks economic tourist attractions.  Evidence from Iceland shows that many areas not in the main tourist areas could be utilized without affecting the underground systems.  Iceland is sat astride the Atlantic Oceanic Ridge (tetonic divergent boundary), and is ideal for geothermal energy generation.  Here super hot thermal vents are piped to the surface where the steam is used to spin turbines generating electricity.  The piped steam and water used is within a closed system and so is recirculated back into the water table at the same level so as to maintain the water pressure and volume at that level, ensuring a sustainable system.

2.  The non-volcanic geothermal, however, is much different since it uses heat variation to generate heat and cooling and not electricity per se. They have been in use for over 60 years already.

If you have ever gone in a cave you will notice that whatever the weather outside the cave, the temperature inside the cave is usually around 56oF.  Once you get about 8 feet below the ground in most parts of the world, the ground temperature remains stable at this 56oF.  Of course in the arctic regions there is permafrost or ice laying over the surface making non-volcanic geothermal impractical.   In utilizing this kind of geothermal, the temperature underground near the surface is used to heat – using a heat pump in cold weather, or cool by direct exchange of cooler underground air in hot weather.  Just like a septic leach field, pipes can be buried in the ground by the home (as vertical loops, horizontal loops, slinky loops, or even pond loops in wet areas) with enough air volume to allow the heat pump to work effectively as an HVAC system.  These pipe systems have a very small footprint for individual home use and are buried under the soil allowing gardens above them once installed.  Neither of the Geothermal energy systems requires any need for combustion products, using only natural energy already in the Earth.

While this renewable energy source seems ideal, it also, like wind and solar, is still not perfect, even if it has no pollution except from the materials to utilize it.

The Positives of geothermal HVAC Generation and Geothermal Energy

Geothermal currently accounts for only about 2.5% of the worlds electrical generation, so has immense potential for expansion.  While being renewable, it is also sustainable since it is a stable continuous 24/7/365 source of energy.  Non-volcanic Geothermal’s best advantage is that it occurs almost everywhere locally, since below 8-12 feet the ground is resistant to the seasonal heating and cooling that occurs in the air around us. A heat-pump is incredibly efficient. Most regular furnaces are about 75-90% efficient at best, while the heat-pump averages 400%. They require less maintenance than a regular furnace.  The initial investment needed to install the ground pipes connecting the house via the heat-pump has a reasonably fast return on investment (ROI).

Volcanic Geothermal electrical generation can be hooked into the electrical grid in the same way as any other turbine produced electricity.  Iceland has shown this works well, cheaply, and effectively.  Whether we can work volcanic geothermal in the western U.S. with the same success is still a work in discussion (se below).

The drawbacks of Geothermal Energy Generation

As inferred above, one of the biggest problems with volcanic geothermal electrical generation is that of siting.  Most of the hot springs in the U.S. tend to be tourist destinations and tapping into the thermal vents may disrupt the course of these springs.  This would be especially true in area like Yellowstone National Park where the geothermal features are a central draw of the park.  In areas using volcanic geothermal electrical generation (e.g. New Zealand, Germany and Iceland) the use of some hydraulic fracturing to expand the thermal vents can cause multiple minor localizes earth quakes.  While only a nuisance, the data from fracking used in Methane production shows these quakes to be of concern.  The current cost of developing a geothermal power plant are about 2.5 times higher than for the same energy produced by wind energy.  In the USA it account for only about 1% of the current total energy.  While it has potential, as part of a portfolio of energy, its high cost and siting issues make it more a longer-term option.  Geothermal vents must be at 350oF to work effectively to produce the steam required for spinning the turbines.  The potential for earthquakes to shift the thermal vent courses make long-term reliability a concern, especially when the generators may be close to tourist areas.  Such geothermal generation would by definition have to be sited in remote areas making both them and the electrical transmission expensive.

As a sum up, using non-volcanic generation with a homes HVAC system is the most optimum use of capturing the Earth’s potential.  Tapping in to the volcanic potential of the U.S. is unlikely to be a firm option in the foreseeable future, although research is on-going to identify technology that can capture this free energy option literally below our feet.

Renewable Energy 3 – Wind Power  

Windmills have been used for centuries, with the first wind turbine for electricity developed in the late 1800’s.  Winds are caused by rotation of the earth, solar heating of the atmosphere and the earth’s surface. We can harness wind energy and use it to generate power as long as sun shines and wind blows.  Wind tower electrical generation is one of the fastest energy, and renewable, generation systems today.  While there are positives and some drawbacks to wind electric generations, it is a lot like solar in that the actual generation of energy is clean with no pollution during or afterwards.  The wind towers however do have to be built and that requires a lot of minerals that need to be mined, smelted and then all used in manufacturing the towers.  The wind blades are made of fiber-reinforced epoxy or unsaturated polyester.  The towers themselves are primarily made of steel – earlier ones as a steel frame tower and modern ones as steel tubular towers.  The turbine, of course has a copper coils – about 4 tons of copper for each MW generation capacity.  If you drive by a wind field you will notice that each tower uses three blades.  This is optimum for minimum drag (reduced wind resistance) and also to prevent (gyroscopic precession – wobbling) although some smaller tower do use just two blades.  Current towers have a life-time expectancy of 20-25 years before they have to be reconditioned and or replaced.

Obviously, when the wind doesn’t blow the tower isn’t generating anything.  Wind turbines work between wind speeds of 5-55 mph.  Below 5 mph they do not have the momentum to start up and above 55 mph the stress of a fast turning shaft can damage the system.  If a high wind above 55 mph do occur then the rotor is locked down.  Newer turbines have gearing systems included in the nacelle (the generator part at the top of the tower) that can maintain a constant rotation speed for optimum efficiency.  The nacelle and blades can swivel on top of the tower to orientate into the wind to capture the maximum amount of energy.   When siting multiple wind towers, the turbulence occurring from the blades has to be taken into account so you will notice that they are evenly spaced where possible – a lot has to do with the land ownership and where towers might be sited.  In some places like Iowa, the towers are more randomly placed as some farmers will not have towers in the land.  Wind fields are specifically located after extensive long-term evaluation using anemometers that measure wind.  The whole of the USA has been surveyed and optimum locations are well established.

The Positives of Wind Energy Generation

It is a non-polluting, clean and renewable source of energy, local, and free.  You only need the technology to capture it.  It is cost-effective with good return on investment (ROI). Each tower has a small footprint (250 square feet) plus a narrow access road.  Once built, the disturbed land around the tower can be reused for farming and grazing.  Land owners can create substantial earning for siting a tower.  The appearance is seen by many as an attractive statement of renewability, although there are those that consider them an eyesore – beauty is in the eye of the beholder.  Currently, wind energy accounts for only about 2.5% of the worlds electrical generation, so has immense potential for expansion.

The drawbacks of wind energy generation

Wind turbines require a consistent source of wind, and even though areas in which they are sited tend to be reliable, calm periods are always problematic.  While wind cannot be a primary source at this time, it can be a major contributor as new storage systems are developed and integrated into the grid system.  The borders of a wind field can be problematic for wildlife, especially birds and bats that can be hit by wind blades as they rotate.  Since wind towers by necessity require open areas the numbers of birds that may be harmed is somewhat reduced.  Wind towers do generate some noise as they cut through the air of about 50 decibels (consider that the tips of the blades may be travelling at 200 mph as they move around), which is about equal to someone talking next to you.  As stated above, they can be viewed by some as eyesores that tarnish the beauty of rural landscapes. Extensive Investment is necessary and ROI may not be fast enough for some groups.  As with any technology that people may object to, there are some fears about safety of wind tower generation.  There is the possibility that the towers could be damaged in a storm and threaten the health of people immediately nearby if the blades tore loose from the nacelle.  Since these wind fields are only economically placed at key wind locations, there are transmission lines needed, but this is true for any electrical generation site.

Current research and development of wind energy generation

One way to reduce bird and bat deaths is locating wind fields not in major raptor areas or migration flyways.  Federal wildlife officials are working with the industry to finalized stricter siting practices.  The use of radar technology helps wind field operators know when flocks or migrations of birds or endangered species that are tagged are approaching at heights below 400 feet (the top height of the blades) the field allowing the towers to be temporarily stopped.  Ultrasonic acoustic signals on the towers have been found to deter bats from entering a wind field zone.  There has also been some dopler signal and bright light research that similarly deters birds, but research is still ongoing.  Other biological research studies show that bats are less active in the wind field zone when wind speeds are above 5.5 meters per second, so wind tower operators can stop the generators with lower speeds without affecting power generation output too much.  Recent studies have found that painting the towers in a variety of colors or painting the blades in red stripes seems to deter birds from a wind field zone.  Of course, we are used to seeing the typical wind tower with three blades, but they do not have to be like that.  There is much research in using vertical axis or FloDesign turbines where the rotors are contained in a housing making bird and bat strikes unlikely.  What is important to note is that much biological research is ongoing to minimize or eventually remove this problem to wild life as the positive potential of wind energy is utilized more.

Renewable Energy 2 – Solar Power  

In reality, nearly all energy on the planet is derived from solar radiation – You know, from that big fusion generator in the day sky, e.g. photosynthesis and wind currents from differential solar heating of the atmosphere and terrestrial surfaces (water, land and ice).  Energy can also be obtained from the planet’s volcanic activity, but while viable and used in some areas Is not a major source for the near future for most of the planet (this latter option will be discussed under geothermal in a later post).

The energy from the sun powers life on Earth and especially photosynthesis that allows life to exist (and a little chemosynthesis).  The potential for humans to capture this energy is immense – consider that each single day on Earth, enough sunlight is received to power human consumption for 27 years at current levels of usage.   Imagine being able to capture it all.  Obviously, we can’t capture it all with current technology, and we really don’t need to, because the sun shines every day, even when it is cloudy and the seasons make the days longer and shorter during the year.  Obviously, some places are better than others to capture sunlight and it goes without saying – yet I feel I need to admit it for those that insist on bringing up the limitation – that its use is limited to daylight hours.

Solar technology is not new. Indeed, people have been utilizing passive solar for thousands of years – Architectural Design uses exposure direction, windows, building materials, eaves and canopies in buildings to maximize capture of sunlight in winter; thermal mass materials that absorb, store, and release heat.  Yet, passive solar design keeps buildings cool in summer through window placement, absorbent materials, air flow, and sun shields to block the sun.  Passive energy is extremely cost effective since it requires no energy to use.  Active solar, as the name suggests, uses the sun in some technological way to focus, move, or store solar energy in some form.  Solar thermal Panels use dark, heat-absorbing metal plates, or heat absorbing solutions in tubes, within in glass-covered boxes, often mounted on roofs for maximum exposure.  Even on a cloudy day, thermal works since it is the ambient temperature that often heats the collection system, although direct sun does make it faster and more efficient.  Visit Scotland or northern Germany and you will see lots of solar thermal heating panels – countries not noted for their long sunny days, especially in winter when the panels still work well.  They use this to warm air within the house, but more often as solar water heaters.  Historically, the first thermal solar collectors were built in 1767 and the first commercial solar water heaters in 1890, so solar has been with us a long time already.

What we typically think about solar energy, we are thinking about active solar using Photovoltaic cells (PVs) that convert solar energy directly into electrical energy.  PV cells work by making use of the photoelectric effect: That is, when sunlight strikes a charged metal plate, the excited electrons migrate through a one-way membrane to another plate.  Like all electricity, electric current is produced by the movement of electrons, and in PVs, the electrons are forced to move along a wire to return to their original source.  One typical kind of PV is when light strikes negatively charged phosphorus, and electrons move from the phosphorus side of the silicon plate to the boron side, creating electric current.  A solar panel is a whole array of these small solar cells.  Since the individual PV cells are so small they can be built to any size ands scale.  You don’t have to cover a roof in Solar PV panels, you can use solar shingles – a form of building-integrated photovoltaics.  These solar roof shingles look like and function as conventional roofing materials, such as asphalt shingles or slate, but producing electricity as well as roof cover.  Commercially, California has been using a solar furnace by having 352,000 mirrors focus heat from the sun onto three water boilers mounted on a tower.  Water in these boilers is turned into steam that then turns turbines to generate electricity.

The biggest advantage of solar is that you don’t need an army to protect or acquire your resource.  It is totally local, and it is also very portable.  Backpackers can carry a small flexible roll-up panel that they can hang from a tree branch to charge small electronic devices they bring in to the wilderness.  In places like Nepal, locals carry fold out solar mirrors, which focus the sunlight onto a central spot to cook or heat a kettle of water.  In many remote rural villages and refugee camps around the world, locals use simple box solar ovens to cook their family meals.  In 2016, a European company used a solar PV powered set of electric motors to power a plane to fly around the world (even covering the long hop from Japan to Hawaii in one flight) at a top speed of 87 mph.  The solar technology for extended options is still in its infancy, but the potential for larger scale use is just waiting for R&D to make some strides forward.  The only drawback of Solar (besides needing sunlight to work) is that the technology has to be manufactured – hence mining, smelting and energy needed for active solar technology manufacture is still a requirement; however, a life-span of 25-35 years means the amount of front end costs (resource needs) is greatly minimized compared to current extraction energy technologies (i.e. Fossil Fuels).  At this time, the cost for solar is competitive to fossil fuels even without subsidies.

Renewable Energy 1 – Hydro-electric Power   

The oldest form of renewable electrical generation is Hydroelectric Power (HEP).  If you take only the electrical generation aspect of this technology then it is clean with no pollution at all – after all it is simply moving water down a gradient over a water wheel that directly spins a turbine shaft generating electricity.  But, like any technology it has full process problems.   The biggest drawback to HEP is of course the requirement of continuously moving water in amounts necessary to spin the turbine shaft.  On the east coast it rains enough that reservoirs constructed behind dams, like the Tennessee Valley Authority project, not only provided flood control for whole watersheds but each dam serves as an HEP plant.  In the west, the aridity of the region meant that water capture behind strategically located dams would capture run off (from winter snow and rain) to serve as reservoirs for irrigation and HEP plants.  Another major drawback for large scale HEP is that the necessary water must come from a major river.  Over the last 100 years or so, nearly all the major rivers in the world have been damned for HEP – there really are no major rivers that can currently be used without major disruptions of local communities and ecosystems.  Indeed, the construction of dams themselves disrupts local ecosystems and because of the natural forces of erosion also condemns the dams to a life-time activity of about 100 years or less.  Silt fills in the area behind the dam and eventually fills in the reservoir.

Environmental Consequences

Besides the sedimentation problem, large dams have as many pros as they do cons.  The pros are that HEP provides clean, non-polluting electricity; flood control; Water storage for irrigation and drinking water, and also opportunities for water recreation (e.g. boating and fishing).  The cons are reduced river flow and sedimentation needs for habitat downstream of a dam; capture of sedimentation behind the dam instead of being spread along the rivers course; alteration and disruption of aquatic life – this often happens because of temperature pollution where cold water releases from the lower  portion of the dam reservoir shocks aquatic life in the lower river; disruption of migrating aquatic species (e.g. Salmon, eels) although fish ladders along the side of a dam can ease this problem; Large scale permanent flooding of arable and recreational land (e.g. Completed in 2003, the largest dam in the world, China’s Three Gorges Dam across the Yangtze River, displaced over 1 million people and submerged Farmland, archaeology, and viable habitat); and one rarely mentioned is the potential of catastrophic flooding from Dam failure.

While over 98% of worldwide rivers are already dammed, in some areas like the Western USA, the amount of water needed to maintain the reservoirs has been declining since the dams were build and because of increased needs for irrigation and drinking water, the storage capacity needed to run the HEP is also diminishing.  This is further exacerbated by droughts many already arid regions are experiencing.

Pump Storage Schemes (PSS)

In hilly or mountainous areas, using excess/unused electricity can pump water uphill through sluice tubes from one lower reservoir to an upper reservoir.  This serves as a form of energy storage and currently worldwide is one of the largest ‘grid storage systems’ available.   When immediate electricity is needed, as in peak-use times, the water from the upper reservoir can be released back down the sluices to spin electric turbines as in regular HEP.  The only difference is that water is in a closed system with the upper and lower reservoirs being linked as storage and usage of electricity.  Obviously, in arid areas, evaporation and other minor leakages means the reservoirs needs topping up a little on occasion.  In wet rainfall areas, the upper reservoir is naturally topped up by runoff.  The amount of electricity that can be generated varies with the size of the system, but it is not unusual for capacity to reach 3000 MW in a single system – roughly equivalent to 3 large fossil fuel stations.  In 2017, the USA obtained over 22 GW of power from Pump Storage schemes.  One of the big problems with PSSs is that they must be located in areas that are usually of natural beauty (i.e. Mountains), which upsets many advocates of outdoors protection.  Options to overcome this are to use areas that are designated as ‘brownfields’ – they are often disused mining areas or areas that have been heavily disturbed from previous activity.  This would stop impacts on scenic or ecologically sensitive areas.

Smalls and Micro scale HEP

In many countries where rain is regular and sufficient, individuals or small groups of houses clustered together can take advantage of small-scale HEP generation.  In areas with riparian rights to running water (if you live by a river you can use it) a minor part of the water flow can be diverted through a small sluice or penstock and into a micro HEP turbo generator before being returned to the river.  If the water is low flow then a Pelton wheel generator may be needed.  While small scale sounds good, it does require a continuous and reliable water source.  Isolated rural communities can capitalize on the small scale HEP.  In arid areas, Prior Appropriation Doctrine of water rights makes this option all but impossible.  Add to that the likelihood of insufficient water capacity in arid areas and small scale becomes only a reality for wet areas with enough vertical drop height to convert the potential energy to kinetic energy with enough efficiency to warrant investment.

HEP has been a great renewable energy option for over a century, but while it generates up to 17% of the worlds electricity it has almost no option for expansion.  Building new dams is expensive and disruptive for a growing human population where arable land is now a premium for agriculture.  The choice of food versus electricity is becoming a real one in many parts of the world.  In many areas where dams have long been a fixture, they are now being removed to allow the rivers to flow naturally again.  The sedimentation problem of dams restricts their lifespan and cleaning out or rebuilding dams is economically prohibitive at this time.  PPSs are still options, but social and environmental pressures will always be a stumbling block.

Introduction to Renewable Energy – A Reality Check

Systems thinking is “a holistic approach to analysis that focuses on the way that a system’s constituent parts interrelate and how systems work over time and within the context of larger systems”– definition).

In the last post I talked about Nuclear Power and that once one factors in the full process for using that source it turns out to be a highly polluting and dangerous source for many reasons – mining pollution, fuel processing pollution, toxic products, waste hazards, potential for catastrophic outcomes, already refined nuclear fuel source potential, and excessive cost to build and maintain.  As an option to Fossil Fuels (FFs), its only benefit is that the generation of electricity is relatively clean of carbon emission and immediate pollution, although the whole process in itself is as bad if not worse, depending on how you measure hazard.  FFs have severe pollution problems from beginning to end, although they are a transportable dense source of energy.  Oil and Gas however have explosive flammability problems during transportation and storage.

Renewable energy is touted as carbon and pollution free, and indeed it is if you only take the generation of electricity into account.  Once you look at the whole process it is still problematic, but the question is to what extent compared to traditional FF and nuclear power.  It is with this understanding that we can look at the options with a clearer perspective.

One of the limiting factors for technology throughout human history is the problem of having enough energy (power) to do anything.  Mainly muscle power with some wind (think sailing ships and Dutch windmills) and some water (water wheels) as the primary option for power – interestingly, all were completely renewable sources, simple as they were once the technology was built.  The main resources were wood frames with some iron strengthening supports and canvas (Hemp) cloth.   The discovery and use of FFs is what allowed the growth of the industrial and then the technological revolutions.

The problem with FFs of course is the extensive mining and extraction, and the even more harmful pollution resulting from using them.  Another problem with FFs is that they are not evenly distributed over the Earth’s surface.  I have always been somewhat amused by bumper stickers that say “Why is our oil under their sand.”  Another unspoken and crucial problem with FFs is the economic stranglehold and control that the businesses that mine and extract the traditional energy have on the world’s economy and how these companies dictate the world’s geo-political policies.    By far the biggest advantage of renewable energy resources is that they are local and non-transferable – you can transport the energy generated but the resources are not something you have to fight to control.

I never tire of hearing antagonists to renewable energy try to impress me with their insights, like how solar panels don’t work at night and wind turbines don’t work when the wind isn’t blowing, yet remain oblivious to the almost insane logistics of providing energy from FFs and dealing with the pollution of the whole system.  From a system’s thinking perspective, renewable energy is a far better source for generating electricity, not perfect, but the many options have multiple advantages over FFs.  I will cover each renewable option in more detail in upcoming blog posts, but for now a simple overview.  The technology we now have has allowed us to tap into the natural resources in ways not possible before the industrial revolution.

We can now manufacture machines that use natural resources such as wind, sunlight, temperature differentials in the ground and in the ocean, ocean tides, etc.  The big kicker here is that the renewable energy capture system must use the FF energy system to get it running at full steam, so to speak.  If we keep waiting and using FFs until they run out, then not only do we have exponentially more pollution to deal with, but the problem of having enough energy to manufacture the required amount of renewable systems will be gone.   After that it would be a remarkably slow process to manufacture enough energy to meet needs even knowing the technology we need to build.

The other big change we will need to think about is how best to tap into renewable sources based on the locality of where it is being generated.  Solar panels in Barrow, Alaska, night be feasible for 3-4 months of the year during the continuous summer sun months, but not much of an option beyond that.  We need to think about multiple sources being used in any locality based on the best management practices of what is available.  And don’t forget, those resources are local – they cannot be disrupted by any body, and the jobs to build and maintain the technology using these resources are always local and cannot be outsourced.  Manufacturing these renewable energy capture systems is the only drawback – they will still require a large amount of mining to get the needed minerals and the manufacturing will still require smelting of the minerals from the ore and energy to build the systems. But once the systems are in place and adequate for the populations needs, then there is no further pollution and no disposal pollution problems.   The truly clean energy can then be used in further manufacturing, with recycling of components being a simple further conservation measure to reduce mining.

More about the specifics of each of the renewables in upcoming posts.

Understanding Modern Energy 4 – The reality of Nuclear Power

Whenever you talk about Nuclear Power, many people think of Nuclear bombs and the like.  Alas, the mere word nuclear is enough to send some people into anxiety.   I love it in the movies when someone is beside a nuclear reactor and screams that the reactor is going critical and everyone runs around screaming in panic.

The other thing I hear a lot is how clean electricity is when it is produced by Nuclear Power stations.  Like most regular power stations, there is a boiler to produce steam, and in a nuclear power station the decay of radioactive atoms in fuel rods inside a closed system stream of circulating water heats a boiler of water that produces the steam to run a turbine to produce electricity (just like any FF source).  Is the electricity clean?  Only if you narrow the focus down to the single fact that there are no polluting emissions when you heat the boiler.   The problem, however, arises from only using that one fact, and not seeing the whole system of generating the electricity – this is also true for renewables, but that is for another post.  For most regular power stations using a steam turbine, the boiler needs to be heated by something.  In nuclear it is water molecules being hit by radioactive decay particles from the fuel rods that excite the water molecules making them hotter.  And curiously, the process for this heating is only efficient when the fuel rod is in a critical state releasing enough particles to do the job.  Otherwise it would just be a toxic fuel rod.  This criticality is what the power controllers look at consistently by damping or increasing the heating through the lowering or raising of carbon control rods that surround the fuel rods.  The before and after process is the story most people ignore.

Mining Uranium

The fuel rods contain Uranium Oxide as the fuel where the natural decay of uranium by radioactive fission heats water.  The rods ability to heat water naturally lessens over time – usually about a 6 year lifespan per fuel rod.  Now that Uranium has to be mined from the ground.  As I have said before, that is an energetic process that generates immense amounts of waste and pollution.  The usual methods of mining can be used (e.g. open pit, underground shaft), but also leach mining where acids are injected into piles of ore on the surface (Heap leaching), or even deep in-situ into specific rock strata (yellow cake).  Once the uranium has been extracted form the ground it must then be processed to enrich it.  Good Ore level uranium is about 0.7%, but must be enriched to about 5% to use in a fuel rod.  This is done through multi-level energetic centrifugation process before the more concentrated ore is further treated to uranium oxide ready for a fuel rod.  As a comparison, however, a 1000 MW coal fired power plant requires about a half million tons of coal a year as opposed to about 30 tons of uranium oxide per year.  We do have the technology to recycle and reuse Nuclear fuel, but it is about as expensive and polluting to do this as dig new ore, but at least this does cater to the one major problem of nuclear fuel – disposal and storage.

Nuclear Waste

The spent fuel rods are extremely toxic and highly radioactive.  This means that they cannot be simply discarded but must be carefully stored on-site at the power plant in large cooling tanks (like large swimming pools).   Since there is no place to permanently dispose of these spent fuel rods – there has been a prepared spot in Neveda  (Yucca Mountain) but transporting the fuel rods there and maintaining security are on-going problems – you don’t want the rods getting into the wrong hands.  After all it is nuclear fuel that can be enriched further for military purposes.

               Nuclear Power Problems

The fuel rods have to be kept at a critical state, but what happens if the rods get to a supercritical state – that’s when you don’t want to be anywhere around.  Super criticality is what is needed to allow a nuclear fuel source to attain a chain reaction if triggered by a specific detonation – booom!!   Fortunately, nuclear power fuel rods don’t become nuclear bombs since there no detonation devices associated with them.  What they can do is become quite problematic when power plants don’t go as expected.  A popular term in the 1980s was ‘The China Syndrome’ meant to describe how a nuclear reactor behaves when it gets super critical and starts to melt.  People perceived that the extreme heat of the melted core would allow it to simply melt its way in the ground and hence keep melting down through planet all the way to the other side.  Of course, that can’t happen because the melted core would eventually reach the inner magma layers and simply blend into the magma.  The reality however, is that the melted core would melt down until it reached ground water layers in the crust.  Then a catastrophic steam explosion would occur and the steam blasting out of the ground would be highly radioactive and move with winds around the planet until it finally settled out or got diluted enough to no longer be a threat.  Notably, nuclear fuel has long half-life’s (the time required for a quantity to reduce to half its initial value) of about 30 years. Some estimates are that the fuel rods can become non-toxic after 159,000 years.  (As a comparison, plutonium has a half-life of 24,000 years).

Of course, in a nuclear power plant there are many safeguards, but the Homer Simpsons apparently do exist.  Three-mile island was a case of shutting of the water surrounding the core.  Once that happened the core started heating up.  Fortunately, it was caught in time and the water turned back on, but not before the top of the core had already melted requiring the permanent shut down of that core.  Rods are designed to be pulled out of place by robotic arms.  The melted mess presented a massive logistical problem.  The Fermi 1 reactor near Detroit suffered a similar situation (that one never really made the news for some reason, just as many other safety ‘near misses’ were never really reported).  Now Chernobyl was more spectacular and widespread.  An unplanned emergency coolant shut off was done, but it coincided with a stream turbine failure resulting in a large fire.  The cores were heating and no one could get the coolant back quick enough.  In an emergency the reactor can be shut down using graphite balls, and as a final desperate measure to completely shut the reactor down, graphite dust.  In most reactors, the core is chambered in a closed housing, but at Chernobyl the containment was apparently open to the sky.  Once the graphite dust had been dumped into the core, the dust was ignited by the nearby burning turbine, and as you might imagine, the reactor core was not only melting but the fuel rods were also burning.  The resulting smoke with nuclear fuel via winds patterns made its way around north-western Europe until heroic efforts by Ukrainian firefighters managed to eventually put out the fire and the cores could be flooded with more graphite dust.   Then when Mother Earth does unexpected attacks like the Tsunami at Fukushima plant in Japan, nuclear core problems become everyone’s problem and for a long time to come.

There are plans for new types of nuclear reactors that are potentially walk-away safe, but the costs involved in planning, building, and maintaining nuclear power stations are extremely prohibitive, especially when compared to renewable options that can provide the same electric power, safely and for a fraction of the investment cost with minimal problems.