Wind and Hydroelectric

Wind Power.

Researchers at Stanford University recently evaluated the potential of wind power globally. After analyzing more than 8,000 wind–speed measurements, the researchers concluded that wind at specific locations could generate more than enough energy to meet world demands. Of the sites measured, over 13% had mean annual wind speeds strong enough for economic electricity power generation (speeds greater than 6.9 meters per second at 80 meters). These candidate sites are found in every region of the world, both inland and offshore. The researchers concluded that global wind could have generated about 72 terawatts (TW) in 2000. This is equivalent to 208 trillion kilowatt hours (kWh) – about one and a half times current annual world energy use. However, wind power generation in practical terms only serves the needs of the utility corporations to supplement supplies distributed by the grid system.

Evaluating the wind potential of the U.S., the Pacific Northwest Laboratory – a Department of Energy (DOE) national laboratory based in Washington state – has estimated that land–based wind across the contiguous United States is capable of producing almost one and a half times current U.S. annual electricity use. According to a recent analysis by DOE, there is also an additional 900 GW of power from offshore wind within 50 miles of the U.S. coastline. This is equivalent to at least 2.6 trillion kWh/yr – almost 70% of current U.S. electricity use.

To produce this much energy, no significant developments in wind technology would be needed. Modern turbines are rugged horizontal–axis three–bladed designs that are turned into the wind by computer–controlled motors.

The power capacity of these turbines has increased dramatically in the last twenty years, from 24 kW in 1981 to 1.5MW in 2006. The turbines have been developed to function at high speeds, high efficiency, and with low stress, which contribute to good reliability. Research on new lightweight composite materials, advanced control systems, and methods for addressing the additional variables involved in offshore sites will only improve the effectiveness of these designs. Counter–rotating horizontal axis turbine designs, which capture a wider range of wind speeds, and vertical axis turbines, which have the potential to generate 4–10 megawatts (MW) per turbine, are also expected to become common in the next five to ten years. The most significant issue facing wind turbines will be the need for appropriate siting and community approval.

It is important to note that wind generated electricity will always be an adjunct to other generating technologies, simply because the wind does not blow in every location all the time and backup supply costs have to be taken into account. Moreover, it does not directly provide for portability for transportation needs..

Economic issues.

A UK Royal Academy of Engineering report in 2004 looked at electricity generation costs from new plant in the UK. In particular it aimed to develop "a robust approach to compare directly the costs of intermittent generation with more dependable sources of generation". This meant adding the cost of standby capacity for wind, as well as carbon values up to £30 per tonne CO₂ (£110/tC) for coal and gas. Wind power was shown to be more than twice the cost of nuclear power.

Without the carbon increment, coal, nuclear and gas CCGT ranged 2.2–2.6 p/kWh and coal gasification IGCC was 3.2 p/kWh – all base–load plant. Adding the carbon value (up to 2.5 p) took coal close to onshore wind (with back–up) at 5.4 p/kWh – offshore wind is 7.2 p/kWh, while nuclear remained at 2.3 p/kWh. Nuclear figures were based on a conservative £1150/kW (US$ 2100/kW) plant cost (including decommissioning).

Present–day (2004) cost of generating UK electricity (p/kWh) from new plant

Hydroelectric

Hydroelectric power currently provides 10% of the electricity generation in U.S. and could be a significant source of renewable energy for distribution by public electricity utilities. Large conventional dams, however, have caused serious environmental damage. They will have to be retrofitted or taken down, while smaller systems with advanced turbine designs are set up (up to 25 MW). According to DOE, advanced systems can be applied at more than 80% of existing hydroelectric power projects, and can also be built at small existing dams that have not been previously used to produce power. Advanced hydro designs reduce the impact of turbines on fish, facilitate upstream fish migration, and mitigate sedimentation and water quality problems. River–run systems – which harness the power of moving water without dams or reservoirs – are also a small, low–impact alternative that could be developed where dams are removed or at new sites. Estimates of potential sustainable hydro resources from existing dams in the U.S. range from 77 to 82 gigawatts (GW). This includes 62 GW from retrofitted existing hydroelectric power projects and 15–20 GW from fitting advanced systems onto other existing small dams. These hydro electric power sources could provide between 337 and 359 billion kWh per year, or 8.5 – 9% of current U.S. electricity use.