A Musing Environment

Solar and Wind Power

How much of a role is there in the immediate future for renewables plus better efficiency? This is the first of three posts on that subject.

The production of wind and solar power is growing rapidly, but that’s rate, not amount. According to International Energy Agency, (unless noted otherwise, most of the rest of this blog is based on the IEA book, Renewables for Power Generation- Status & Prospects):

This table overestimates electricity production worldwide — I couldn’t find capacity factors for world; US values are higher.

* US capacity factor values (from Nuclear Energy Institute) are used, rather than world values. To obtain kWh, multiply GW by 24 x 365 x capacity factor. Divide by 1,000 to get units right. Capacity is lower than 100% for solar because the sun isn’t always up, and because the sun’s rays aren’t always perpendicular to the photovoltaic (PV) panels. Wind power capacity is less than 100% because the wind is not always blowing; in particular, there is often little wind on very hot or very cold days. Estimates on kWh produced by each technology are probably high. For example, the capacity factor for German wind is about 20%. The capacity factor for European PV panels is also likely less than US values, as much of Europe is north of California. The latitude for Rome is 42 N, while New York City is 41 N.

More on Solar

Thin Film PV. Some are optimistic that thin film PV is the cheaper technology of the future.

PV panels break even on energy in 2 – 5 years; at that time they have produced as much electricity as was required to construct the panel. They last 20 – 30 years (after which they still produce electricity, I think, just less — someone told me that they deteriorate by 0.5%/year), but inverters and batteries must be replaced every 5 – 10 years, more often in hot climates. Producing PV panels requires toxic metals, but they appear not to be getting into environment and human body via production or waste. Prices and use of toxic metals are going down, efficiency is going up. They work best in areas with large amounts of sun, and expensive daytime power. At some point, land use may become an issue; but

(b)uilding stock in industrialised countries offers enough suitable surfaces for PV to generate between 15% and 50% of current electricity consumption.

This will be less than 15 – 50% of 2050 consumption under even the most optimistic population and efficiency improvement scenarios.

PV Integrated into Roof Shingles

Much greater investment in research and development is crucial. Independent of climate change, investing in solar is investing in cheaper electricity tomorrow.

For information on solar lighting (using optical fibers to light with sunlight), solar hot water and space heating, and more on solar power, visit the National Renewable Energy (NREL) solar site.

More on Wind

Windmills are growing in capacity, with new wind turbines in the MW range.

The intertwined problems of intermittency and impacts on grid reliability present two of the strongest challenges to wind energy’s future prospects. When wind is providing too much or too little power, the reliability of the grid is affected. Because wind is based on natural forces, it cannot dispatch power on demand. Because utilities must supply power in close balance to demand, intermittency can limit the amount of capacity of highly intermittent technologies that can be integrated into the grid. Thus, as the share of wind energy increases, integration of wind turbines into the electrical network will need both more attention and investment.

In Denmark, some local regions in Spain, and in Northern Germany, penetration rates of over 15% (and even up to 50% for a few minutes) have been seen. In some instances, this has caused grid control and power quality problems, but not in other cases.

Wind turbines located offshore and in mountainous terrain are subject to potentially very high costs for O&M and loss of availability due to climatic influences.

This is likely to be a problem for hydroelectric power in some areas.

NIMBY is putting increasing pressure on windmill placement both in the US and Europe.

Note: wind prices will decline with technology improvements, but at some point, wind expansion will only occur if less windy regions are used.

Wind power causes local climate change; this may be good or bad for the region.

For more on wind power, visit the NREL wind site.

The IEA book also reviews small hydropower, biopower (using plants to make electricity), geothermal power (not technically renewable), and concentrating solar power (to heat water, then combine with biopower or natural gas). NREL has information on these and other technologies.

Biopower and small hydropower were each of more importance than wind in 2000. But wind power growth is so rapid that by 2010, the majority of the installed capacity from these systems is expected to be from wind (though not the majority of the electricity production because of the lower capacity factor.)

Storage Systems for Solar and Wind Power

Neither wind nor solar power is considered base load power (on all the time). They operate with either hydroelectric or natural gas backup. In areas with more wind at night, the electricity produced may be wasted.

It is not likely that solar will provide base load power for decades, if ever. (Batteries are expensive and polluting.) A storage system for wind power, compressed air energy storage, is being tested at a couple of sites, including Connecticut, and has been proposed elsewhere, including Iowa. During times of peak electricity needs, natural gas is blended with the compressed air; the mixture then drives a natural gas turbine.

Argonne National Lab looks at salt caverns appropriate for storage.

Compressed Air Energy Storage in Salt Cavern

A later post (the next?) will look at improvements in efficiency.

This entry was posted on Thursday, December 7th, 2006 at 11:00 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.