Least we overlook the obvious, the sun doesn’t always shine and the wind doesn’t always blow; but the demand for electrical power remains. As we rush headlong into the quest for renewable, non-polluting energy it is, perhaps, prudent to review the place of such alternative energy sources as wind and solar in the total energy system.
Solar and wind power technologies are both low efficiency producers of power, converting only a relatively small percentage of sunlight or wind into usable energy; and both suffer from variable and unpredictable availability. Thus we have relatively inefficient, unreliable supply balanced against a relatively constant demand for reliable energy. This is not a good match, and not one that we can rely on. In fact many instances of peak electricity demand occur during periods when supply from solar or wind are low, or non-existent. On a regional basis, there are only two viable alternatives to this dilemma: standby and storage.
The most common application of the “storage” concept is “pumped hydro storage” in which electricity generated during periods of slack demand is diverted to pump water into a high elevation reservoir. During periods of high demand water is released from the high reservoir and passed through turbines to generate electricity. A relatively old technology, pumped hydro is most commonly used for “load-balancing” with water pumped into the high reservoir during the night, and released through the turbines during peak-demand daytime hours. Pumped hydro is restricted to hydro-electric facilities in sites permitting an elevated reservoir, which is not often the case. Due to the energy required to pump water uphill into the high reservoir more energy is actually used than produced, but since utilities can charge a higher rate during peak demand hours, pumped storage facilities can be profitable. Batteries, flywheels, compressed gases another other schemes for storage may have limited applications, but are not feasible on a regional basis. Some will content that wind and solar power are actually a variant of the storage concept as they permit the “storage” of fossil fuels when the sun is shining or the wind is blowing.
The alternative to storage is a standby conventional generating facility maintained in a constant state of readiness and prepared to instantly assume the load if solar or wind power becomes unavailable. To be effective the constant standby facility must be in a “spinning” state with its generators rotating at production speed. The standby facility constantly consumes energy and must be staffed and maintain as if it were a full-time production facility. While the energy consumption of the standby facility is less when it is in a standby state than when actually producing electricity , the emissions required for the construction, maintenance, operation, and the ultimate demolition and disposal of the duplicate facilities must be accounted for in determining the effective emission reduction of solar or wind power.
Wind and solar advocates often envision wind, or solar, farms in geographic regions that are rich in these resources, and with the generated electricity fed into regional, or national, grids for distribution to distant locations. In theory such a scheme would be equivalent to the load-balancing of pumped hydro on the if the wind is always blowing, or the sun always shining, at some location on the grid. Unfortunately, no national grid is that large, and world-wide grid capacity and construction has not kept pace with increased demand. Also, in most regions, distribution grids are at, or near, capacity with increasing brown-outs, or black-outs a near-term possibility. The grid capacity for simply transporting energy from producer to consumer, in-lieu of local generating facilities, is virtually non-existent
Solar and wind certainly have a role in supplying needed energy, but it is hard to imagine that they can ever be more that a supporting player, not a core contributor. It would seem reasonable that large-scale government funding for solar and wind development would be far better spent on increasing the efficiency and reducing the emissions or our current fuels, and seeking new technologies whose supply is more reliable and capable of matching demand. The fact remains that the most economical, reliable, readily available and zero-emission alternate-power source is conservation!
