Panos Prevedouros, a professor of engineering at the University of Hawaii
Panos Prevedouros, PHD, professor of Engineering at the University of Hawaii

BY PANOS PREVEDOUROS PHD – This brief analysis is a simple case of a picture is worth one thousand words.

The GREEN line is our house’s monthly electricity consumption which averages about 450 kilo-watt-hours or KWh.

The ORANGE line is our house’s monthly solar panel electricity production which averages about 250 KWh.

To make them directly comparable both averages were normalized to the level of 100. Also these were further smoothed to account for HECO’s accounting variability because some monthly bills include as few as 28 days or as many as 33 days. So power consumption was estimated on a per day basis and then converted to a monthly basis.

What is there to observe? Simply that the solar (renewable electricity) production profile is not at all in tune with our household’s monthly electricity consumption. Humid days call for more A/C use, Christmas celebrations call for more lights and cooking, summer months take us to vacations or time away from home, but the sun’s trajectory and cloud density do not follow any of these habits.

The lesson on a grand scale is that a city, state or country cannot possibly depend on renewables such as wind and sun for more than a small fraction such as 10% for its power generation because of significantly negative productivity, health and safety implications.

One must be a great fool to believe that the large deviations shown in the graph (which can be extreme on an hour-by-hour basis) can be covered by … batteries.

On the other hand, renewables from geothermal, nuclear and tidal wave harnessing are in a different class and can offer base-load reliability that covers the fluctuating needs of a large population concentration. But even them they need supplementation by true base load power generation from nuclear, coal, oil or natural gas power plants. As mentioned in an earlier article, waste-to-energy for Maui, natural gas for Oahu and geothermal power plant development on the Big Island are best near term choices for Hawaii.