Water has many potential uses for generating energy. The most common water based power generators are hydroelectric dams, also called “large hydro”. There are also “small” and “micro” hydro plants in use in remote locations where water is plentiful. Hydroelectric power accounts for around 3% of the world’s energy. An example is the Hoover Dam pictured above (from Wikipedia).

Hydroelectric power makes use of the potential energy stored in dammed water using it to drive a turbine and generator. The amount of energy extracted depends on the volume of water in the reservoir and the height difference between the source and the outflow (see picture on left). Hydroelectric is renewable since rainfall adds water up-river which ends up in the reservoir until it is released to generate electricity. Aside from building the dam and plant, the energy production is clean and low-cost. However, these dams can cause other environmental damage by changing the natural waterways. Some side effects include accelerated erosion, reduction of fish spawning, and water quality changes (e. g. depleted oxygen and elevated temperature). Hydroelectric dams provide fairly clean, low-cost and predictable energy, but they do have adverse effects and viable water sources are limited.

A burgeoning area of water power generation involves waves and tides. Wave power makes use of the kinetic energy in the rise and fall of waves in the ocean. A European manufacturer (as described on ZDnet), Pelamis Wave Power, makes the Wave Energy Converter (WEC). The Pelamis WEC (pictured on right) makes use of several cylindrical sections linked with hinged joints. The wave-induced motion of the joints is resisted by hydraulic rams which pump high-pressure fluid through motors which drive electric generators. California’s PG&E is investing in the United State’s first “wave park” off the coast of Eureka, CA. This installation will make use of Finavera Renewables‘ AquaBuOY (pictured on left) to generate 2 MegaWatts of electricity. For more information on the AquaBuOY technology, check out their video or read about this deal on GreenWombat.

Tidal power makes use of the rising and falling of the water level due to tides. One way to do this is to capture water at high tide in a basin, then discharge it near low tide through a turbine. This method, also known as a barrage, has been used for a thousand years in the form of tide mills for grinding grain. Another alternative, called tidal stream power, utilizes turbines installed underwater in tidal channels. PG&E, the City of San Francisco, and Golden Gate Energy are conducting a study to assess the possibility of harnessing the tides in San Francisco Bay (from Green Car Congress) using a device like the Lunar Energy RTT Turbine (pictured right).

Ocean thermal energy conversion (OTEC) exploits the temperature difference between the warm surface and colder deep waters. The process uses something called a heat engine. A heat engine uses a device placed between a hot reservoir and a cold one. The engine extracts some of the heat in the form of work. A common example is a steam turbine where fuel is burned to create steam, which turns a turbine, and then condenses back to water to be recycles. The OTEC concept is the same, but the fuels is the sun warming the surface water, a low boiling-point fluid like ammonia is used as the steam, then deep sea-water is used to cool the ammonia back to liquid (see diagram on left). Unfortunately, the OTEC engines are not very efficient and the ocean locations with large thermal differences are limited.

The final water power technology is called osmotic (or Blue) energy. It uses the difference in salt concentration between seawater and river water to generate energy. The technology relies on osmosis through methods such as Reverse Electrodialysis (RED) and Pressure Retarded Osmosis (PRO). Osmotic energy technologies are still in early stages of development, primarily in Norway.

There are quite a few water power options. It seems like hydroelectric dams are fairly saturated and cause their own environmental problems. Wave and tidal power look pretty interesting. They should be more predictable than options like winds and solar. I wonder what sort of impact these technologies will have on marine life and shipping. Osmotic power also has potential, but it has a ways to go before it is economically viable. It certainly seems as if energy from the big blue can be green.

A friend of mine sent me a link to a web site called The Story of Stuff with Annie Leonard. The site contains a 20-minute animated video describing the “consumer economy” and it’s effects on society and the planet. The bulk of the video is pencil-looking animation mixed with live shots of the host, Annie Leonard. Annie has spent more than 20 years investigating factories and dumps around the world. She has a lot of experience in international sustainability and environmental health issues. The video is both entertaining and troubling at the same time.

The Story of Stuff describes the product life cycle as: extraction, production, distribution, consumption and disposal. As part of my experience as a contestant in the California Clean Tech Open, tried to better understand the environmental impacts of the product cycle. The main problem with the existing paradigm is that the process is linear and open-loop. Basically, we’re taking all the useful stuff from the planet and replacing it with harmful stuff. The goal of sustainability is to close the loop on the system through reuse and recycling as well as reducing the harmful side-effects along the way (like pollution and deforestation). As someone trying to start up a sustainable cleantech company, I am very concerned with ideas such as Design for Environment (DfE), Life Cycle Assessment (LCA), and Cradle to Cradle (C2C).

Another major problem with the current paradigm is the sheer amount we consume. We in the US are especially driven to have all the latest and greatest stuff. We’re “good consumers.” We’ll even buy new stuff to replace perfectly good, though slightly out-dated, stuff. This is causing us to use up our resources even faster while creating more and more waste. Moderation and conservation are principles each of us needs to apply to our lives. “Good consumers” may be good for the economy, but we’re bad for the planet.

The video barely touches on the alternative, but the website provides some ides on how to make a difference in the section called Another Way and there’s a blog on The Story of Stuff for updated information. It’s a big problem and there’s no simple solution, but there are many ways we can get involved and make a difference. It’s about time we start. We only have one world to live in; we need to treat it with respect.

Biomass refers to living and recently dead biological material. It can be used as an energy source directly, such as by burning, or to produce a biofuel, such as ethanol. Biomass accounts for 4% of world wide energy production, much of this in developing countries which burn wood, charcoal and other materials for cooking and heat. However, a lot of research is going into biomass-based energy, especially in the area of biofuel for transportation.

Biomass is a renewable resource since crops can be planted again and again. It is also thought to be carbon neutral since the carbon released during energy conversion is absorbed by new plant growth. In practice, biomass is not truly carbon neutral, since energy is required to grow crops and convert them in to fuel, though it is generally an improvement over fossil fuels. However, recent studies indicate that the advantages of reduced carbon emissions of crops such as rapeseed and corn may be more than offset by increased nitrous oxide emissions which has a much higher greenhouse effect [Source: EnviroStats].

There are other negative impacts of using biomass for energy. One is that some biomass sources, such as corn, are also major food sources. This can potentially lead to food shortages. Another issue is deforestation to create cropland. It is often the case that the biomass crop absorbs less carbon than the forest it displaced, causing a net increase in carbon dioxide.

Energy from biomass waste is an interesting prospect. Converting municipal solid waste, farm waste and other biodegradable waste streams to energy could reduce global warming as well as reduce pollution and waste stream management problems. Landfill sites generate gases such as methane. Capturing this methane and using it as a fuel source can also reduce emissions of greenhouse gases. Waste may not meet all of our energy requirements, but not utilizing this energy source has a negative impact. The University of New Hampshire is the first university in the country to use landfill gas a primary energy source [Source: Earth911].

Biofuel sources range from simple vegetable oil to bio-engineered algae. The primary focus has been to replace gasoline and diesel in transportation. While corn-based ethanol has had a lot of support in the US, it also carries a lot of negatives [see Energy Roundup]. Biodiesel has a lot of potential [see Green Myth-Busting], but diesel engines are not common for standard cars in the US (though could be a benefit to trucking). Butanol, which is claimed to be a direct gasoline replacement, is another potential biofuel that has received some high profile investment lately [see Green Wombat]. In the meantime, companies like LS9 and Amyris Biotechnologies are trying to engineer bacteria which can produce a gasoline substitute from biomass sources [see Greenstock].

It seems to me that our energy future will come at least in part from biomass.

As I mentioned in “What’s the Alternative?“, Nuclear accounts for 6% of world wide energy production, the largest source after all the various fossil fuels. Nuclear is not a form of renewable energy, but it is a potential alternative to fossil fuel. Nuclear has a bad reputation, primarily due to potential hazards of the power plant and the waste, as well as the fear of nuclear weapons. I don’t believe these issues are sufficient to rule out a nuclear future.

Modern day nuclear energy utilizes a controlled fission reaction to generate heat. The heat is used to boil water, generating heat. The heat is used to drive a steam turbine which generates electricity. Fission is the splitting of an atom caused by striking it with neutrons. The splitting of the atom releases energy and additional neutrons which may strike other atoms, causing a chain reaction. The chain reaction is controlled by using materials that absorb (cadmium) and moderate (water) neutrons. A diagram of a light water reactor (LWR) can be seen below.

Thermal Reactor Diagram [Source: Wikipedia]

The most common fuel source for nuclear fission reactors is uranium-235. Naturally occurring uranium is less than 1% uranium-235, the rest being uranium-238. To maintain a sufficient chain reaction, most uranium is enriched to 3-4% uranium-235. One gram of uranium-235 has the energy potential of 3 metric tons of coal [Source: IEER]. The US currently produces 20% of its energy using nuclear power and France uses nuclear for 80% of its power. According to the Energy Blog, China is planning to quadruple their nuclear power by 2020.

One of the primary concerns with nuclear power plants is safety. There have been accidents at plants resulting in radiation contamination. The worst commercial nuclear reactor accident in the US, Three Mile Island (1979) is said to have produced less than 100 millirems of radiation exposure on site (less than annual exposure due to natural sources) and 1 millirem of exposure to nearly 2 million people ( a chest X-Ray is about 6 millirems). [Source: US Nuclear Regulatory Commission]

The destructive power of nuclear weapons also feeds the fear of nuclear power generation. A nuclear weapon utilized an uncontrolled chain reaction of weapons-grade uranium. Weapons-grade uranium is enriched to over 85% to achieve such a devastating result. Enriching uranium to weapons-grade level is not a trivial process, although knowledge of the enrichment process for nuclear power generation could lead to the knowledge of achieving weapons-grade uranium. Or so it is feared.

Uranium is a fairly common material in the Earth’s crust. While uranium-235 produces much more energy than coal, a lot of uranium ore is needed to produce the necessary uranium-235. However, many studies have shown the indirect emissions from nuclear power generation are many times less than fossil fuel plants. Nuclear generation does not produce most of the pollutants associated with the combustion of fossil fuels. Spent rods can be reprocessed to recover 95% of the remaining uranium, but the technology to achieve this is still in it’s early stages. France, the leading reprocessing country, recovers 28% of their spent fuel. The rest is placed in secure storage with the hope that the technology will arise which can reprocess the material further.

Nuclear technology continues to improve. Continued improvements in reactors and reprocessing will make nuclear even more viable. Research is still ongoing in the ever-elusive area of fusion reactors, which theoretically use and produce fairly harmless material, but they are not yet viable. In the mean time, concerns for safety will most likely relegate nuclear to a small role in world-wide energy production.