Long term solutions to power society should be sustainable, clean, safe, and affordable; but all of these descriptors are relative. Sustainable has the least wiggle room in its definition. Fossil fuels which took 100s of millions of years to accumulate, but are being consuming over a century or two obviously don’t qualify. For that matter they are neither clean, safe, nor affordable if consideration is given to all the hidden costs of health care and environmental degradation.
Large hydropower facilities are generally thought of as clean and affordable, but how about sustainability and safety? Large scale hydropower sites, dams with lakes behind them, don’t exist forever. Depending on the facility, life spans of 50 to 100 years seem to be an average. The reason is simple, rivers carry more than just water, they also move silt. Eventually the dam site will fill with silt. After time silt accumulates, filling in the reservoir.
The silt can be dredged out but that can become a large expense, impacting affordability. Hoover Dam, because of it size, and more importantly the silt trapping effect of Glen Canyon dam above it, has a projected life time of several centuries.
What about dam safety? Actually catastrophic failures are not unheard of. In the last 10 years in the United States alone close to 200 dams have failed. Obviously living downstream of a dam is not the safest place to be. One dam failure in 1975 in China resulted in 26,000 deaths due to flooding and another 146,000 deaths due to illness and famine.
Nuclear power is considered by some to be a sustainable energy supply, and as long as everything operates as it should it can be clean and safe. Nuclear power however suffers from the risk of catastrophic consequences when things go wrong.
Three Mile Island suffered a partial core meltdown with minimum release of radioactive material. Three million people live within a 30 radius of the site.
A reactor in Chernobyl, Ukraine caught on fire and burned uncontrollably for days, spewing radioactive material for hundreds of square miles. Radioactivity set of alarms at a reactor site in Sweden within two days.
Damage due to a tsunami caused failure of several reactors at Fukushima and the problems are ongoing. A radioactive plume of seawater is making its way across the Pacific Ocean towards the west coast of North America.
So we are left with wind, solar, and geothermal. They are all sustainable, clean, safe, and compared to the real costs of the alternatives affordable. An especially attractive aspect of these sources is that they are quite diffuse compared to the aforementioned alternatives. Nobody will knock out the grid by flying a plane into tens of thousands of solar arrays, it just can’t be done. A terrorist might take down one wind turbine, but not hundreds in a wind field.
Any centralized power plant can be a target for terrorism. Our energy supplies of the future should be sustainable, safe, clean, and affordable. We should add distributed to the list as very unlikely targets for terrorism.