Renewable energy is not a new concept, people have been using it for thousands of years. Solar heating, geothermal heating and cooling, water wheels, windmills, sailboats, etc. These were our primary source of energy until we found the uses of oil and coal, which took over because of their (originally) extremely low cost and portability due to their energy density. Fossil fuels were also a much more effective way to make money than renewables were, because while renewable energy keeps replenishing itself, fossil fuel dependency meant that they could keep selling more on a regular basis since people constantly ran out. Currently, there is much speculation about the cost of various forms of renewable energies in comparison to gas and coal. It is a somewhat complicated issue; fossil fuels are quite cheap but have many environmental costs (mostly ignored and there is uncertainty about some additional side effects) and the prices will simply continue to rise endlessly as we approach and pass peak oil (peak oil is when oil production globally hits the maximum speed we can harvest, afterwards our oil supply will slowly wither away. Renewable energies have a high initial cost, but have virtually no costs as time goes by aside from occasional maintainence because their fuel is free and never goes away. Renewables have another unknown factor because the technologies we are using now are so new, we don’t have any good examples of how long solar panels, wind and tidal turbines, and such will continue to operate. All we know, is that they all last quite a long time.
Solar Power-
Solar
power is arguably the most popular form of renewable energy. This is partially due to the fact that there are so many different ways of harnessing and using it. Solar power can be harnessed in a number of different ways. The two basic forms are photovoltaics and solar thermal energy. In most countries, when solar power is mentioned the average person immediately thinks of a photovoltaic solar panel, which is a very recent introduction in the field. Solar thermal power has been utilized for thousands of years, beginning with such humble roots as choosing or building a home that lets the sun in during the day to warm up to simply setting things out in the sun to dry, cook, or warm. ”Passive” solar heating is probably the most common and underutilized form of solar power, that is the simple idea of designing a building to use the sun for heat when it is cold outside and using shade to keep cool during the hot months. Solar thermal is also becoming popular as a form of water heater. This is another ancient use, but modern systems consist of black pipes laid out in the sun filled with oil which circulates through the tube and indoors to radiate the heat into a tank of water either for preheating or as the sole heating unit. The same basic setup is also sometimes used for heating the air as well, although that is much less common. One of the newer methods of harnessing solar thermal power is the solar thermal electric plant, which has it’s basic roots coming from a water pump designed in the 1800′s that was used for irrigation. These machines consist of reflectors (mirrors of one sort or another) that concentrate sunlight on a centrally located steam(stirling) engine. Once the water is converted into steam, it is used to pump the pistons of the engine which turn a crankshaft connected to a generator to make electricity. Currently photovoltaics operate at approximately 20% efficiency for a standard style unit and 12 to 14% for thin-film modules. The output of photovoltaic panels can be increased by approximately 30% if mounted on a pole and outfitted with sun-tracking motors. Solar thermal generators operate at above 30% efficiency but are used less extensively because they only work well in warm climates with very plentiful sun, require a larger area for collection, and require fresh water. Solar thermal heaters have a larger variance but can have efficiencies of up to 90% or more in some applications. The primary complaint that people have about solar energy is habitat destruction, such as with the desert tortoise in California. This issue can be mitigated by carefully choosing solar thermal sites, and using photovoltaic panels on available roof space or elevating them above ground if fitting roof space isn’t available.
Wind Power-
Wind energy is the second most ubiquitous form of renewable energy has also been around for a very long time. Among the first uses of wind power was the sailboat, but the windmill is what sticks in people’s minds today when it is mentioned. There are two basic styles of wind turbines, horizontal axis and vertical axis. Horizontal axis turbines are by far the most common, they are recognized as “propeller” type designs. Vertical axis turbines are generally tall and thin and have a spiral shape blade design. The primary factors affecting the production of wind turbines depends primarily on average wind speed, elevation (height above the ground/trees/buildings), and fetch (distance upwind that is clear of all obstructions). Most turbines increase in efficiency in winds up to 10 mph or beyond, and have an automatic shutoff when the wind reaches speeds that may become dangerous and/or damage the turbine. Larger models will activate a braking system and eliminate the angle of interference of their blades. Larger turbines and vertical models are generally much more efficient in lower wind speeds, small turbines often need winds in excess of 20 mph to generate their claimed electrical output. Detractors of wind energy cite studies that demonstrate birds and/or bats flying into spinning blades which can reach speeds well in excess of 100 mph. It has been found that properly placed turbines/wind farms have little effect on bird populations, the early studies that found issues were based on wind farms that were placed in the middle of migratory pathways (these issues have been remedied, at least one farm I know of bought many square miles of land to provide a new migratory corridor for the birds). Bats have proven to be a more difficult issue, primarily in the Pacific northwest. Scientists are working on a solution, but it is complicated by bats’ use of echolocation instead of sight and sound (they are confused by the speed of the spinning turbine and have difficulty detecting the blades). These problems can be further remedied by using turbines off shore, erecting solitary turbines (which does reduce efficiency to a degree), and other tricks such as placing lights and whistles on spinning blades.
Water Power-
One of the earliest and most common forms of electricity production using renewable energy is water power, which works along the same basic idea as wind power. The most well recognized example of water power is the hydroelectric dam. While both wind power and water power work by using the flow of “fluid” matter, wind power is dependent on flow alone, while water power primarily takes advantage of gravity. The basic equation for water power is mass times change in elevation equals output. When a water supply is fully controlled, as in a dam, it is very efficient in terms of output because no water is wasted and the speed can be optimized to the turbine’s maximum efficiency. Dams, however, are falling out of favor because they are extremely damaging to the environment, both flora and fauna. Partial dams are not as effective but because they only divert a portion of the water and don’t greatly impact the speed of flow, they cause comparatively much less environmental damage. Newer forms of water power are tidal, current, and wave energy. Tidal power is virtually identical to partial dams except, of course, it is dependent on the tides instead of a river. Current power (utilizing the power of ocean currents) is basically identical to wind energy, but for being in the ocean. Wave energy is a new concept, and there are two basic methods of cultivation. The first is the oscillating water column, which is used at or near the shoreline. This design uses the up and down of the water to compress and decompress air, pushing it through a turbine (not all models generate electricity upon decompression). Off shore generators use various types of flotation devices to capture the motion of the waves, a “duck” system that alters it’s orientation when a wave comes, a hinge system which makes energy at the joints connecting multiple floats to each other, or a simple float that pulls upward when lifted by a wave. Wave energy is fairly new, and so there are many new ideas constantly trying to get into the spotlight. Tidal and current turbines may pose a threat to wildlife, but the technology is still new and still being tested for any collateral damage it may pose to wildlife. Any system which is moored to the seabed may cause damage to any coral or other life on the ocean floor at the time of installation.
Biofuels
Biofuels have also been used by people for millenia, after all, it’s what we eat. The earliest conventional use of biofuels commenced with the “discovery” of fire, and has been used as such ever since. Even fossil fuels are technically a form of biofuel. Aside from burning wood for heat or cooking, the most prevalent biofuel is ethanol, sourced from corn. This has given biofuels a bad name, because between land use alterations, planting and harvesting, spraying of pesticides, and distillation and refining, it has a larger carbon footprint than gasoline (and less power density). New types and methods of procurement are aplenty, though. Ethanol is also being made from sugarcane, beets, and many other food crops. It is made from the starches of the plant and/or, preferably, the undigestible waste cellulose (currently used in many countries for electricity production). Algae is likely one of the most promising biofuels that has yet to hit the market. It is able to produce harvestable oils at 3 times the density per acre compared to conventional crops, can be grown in saltwater, and it’s tank can be connected to a power plant’s exhaust as a filter and a way to trap carbon dioxide. Two more very promising biofuels come from waste products as a bonus. Biogas is methane from sewage, human waste and waste from farm animals such as cows. Biogas has the added benefit of converting methane, one of the most potent gases in global warming, into carbon dioxide, which is about twenty five times less potent. Lastly, there is syngas, which is produced by the gasification of biomass. In this scenario, biomass is superheated in an oxygen deprived environment (pyrolysis), breaking down into hydrogen, carbon monoxide, and some carbon dioxide and methane, which are then used as fuels. This results in much less pollution and lower levels of carbon dioxide exhaust than normal methods of burning the same materials. Pyrolysis can also be used at lower temperatures to create heat and leave the carbon behind as biochar, a very potent fertilizer. This method was originally developed by indigenous populations in the amazon, long before Columbus came to the Americas.
Unity in Diversity
While there is much infighting between proponents of various types of renewable energy, it is important to note that we need all of them. Solar only makes power when and where the sun shines, wind power only works at certain wind speeds, tidal power ceases at high and low tides, etc. Since renewable energy doesn’t produce power on demand, as fossil fuels do, we need a balance to keep the flow steady and as balanced with our energy consumption as possible. There is also substantial power loss as electricity travels longer distances. People are currently hard at work to develop a smart grid to better manage the flow of energy, but even that won’t be enough; we must also continue to develop storage methods. Great strides are underway in battery technology (although the electric vehicle market may well end up using most of those), solar thermal plants can store energy in molten salt, simple mechanical gravity based batteries may be used, etc. This is currently the most rapidly changing part of the renewable energy field, there are so many possibilities which are constantly advancing, it is difficult to know which technologies will win out in the end. And, of course, I can’t finish this without reminding you that going for a walk or a bike ride can do wonders to help the health of both the world, and yourself.
