We are solar powered

Many of the energy options in the WilderHill Index are technologies that we not only address in a technical sense, but also utilize everyday. We believe practical knowledge-gained can assist in discussing clean energy ahead. For example we are intimately familiar with how solar power may be sensible today. This is more than theoretical; at our 1-acre San Diego site, we utilize several different systems to:
  1. generate electricity and
  2. provide all building hot water.

For example we're harvesting considerable electric power from the sun via solar PV (PhotoVoltaic = electricity generating) panels. This array is 'grid-intertie' meaning our buildings are connected to the power-grid; during daylight hours we're generally making much more power than we consume and automatically 'sell' power back into the grid. Thus in daylight our electric meter actually runs backwards. At night it's reversed; we 'buy' power from the utility-and the meter runs the opposite direction. Grid-interconnect means we're able to avoid cost of batteries while it allows rebates by the State of California. As shown next for the solar PV costs, this solar PV performs well in cost/benefit projections, return on investment, and in practice.

This 3.85 kilowatt (kW) solar PV system is calculated to achieve payback in approximately 10 years (see solar PV system costs). This short time to our payback is mainly due to *California State solar subsidies, and *the application of time of use metering by our local utility. Certainly, the upfront costs for the system were significant. However we estimate after generating solar power for 10 years, we'll have recouped a full return on investment and so thereafter most of our electricity is made at no charge. That stability contrasts with highly dynamic electric utility rates that usually go up over time, and it smartly will go on for years after cost amortization. Solar panels are the main cost and they carry a manufacturer's Limited Warranty of 25 years — notably a longer panel life is expected, given the performance of old panels in service for decades. (The single 3.85 kW Inverter carries a shorter life and it will have to be replaced). We expect to see years of profitable PV operation and thus feel without any undue sentiment, that this can be a sensible return on investment.

So far this innovative system has been noteworthy. In 2003 we installed 21 then-new Sharp 185 watt panels (see spec sheet) in three strings, with a 14.2% module efficiency rating. The panels made in the USA are among the most efficient in a consumer product, employing a rather unique and power-dense mono-crystalline design. The panels were matched with a Sharp Sunvista 3,500 watt inverter (along with two web-based real-time monitoring systems) in one of the first such applications then in California.

As illustrated by daily monitoring data in detailed graphs, we're obtaining module efficiencies of ~5% to 10% over the manufacturer rating. Inverter efficiencies are also measurably high and in spring to summer we can generate over 20 kilowatt hours per day. During winter months, with fewer daylight hours and less irradiation overall, we generate perhaps half that amount.


Solar PV panels being installed, 2003

Besides solar PV for electric power we are using two different solar water heating systems. Both are thermal and so rely on collecting and focusing the sun's warmth to heat water. First there's a small primary system that's completely passive and does not require pumps thus increasing overall efficiency; this also extends expected system life. A larger secondary system uses an AC pumping motor (powered by the PV array+inverter) when other hot water is needed. (We are in planning for separate PV solar panels that efficiently run on a DC motor, simply pumping water to the heating array automatically when the sun is shining).


Smaller, passive thermal water heating
Larger panels for heating pumped-water.

We monitor building energy demands too-as well as power generated-in part because it's as useful to reduce demand via efficiency (and avoid need for much power in the first place), as to is to make energy renewably. Several solutions have been brilliantly simple. We e.g. use compact fluorescent lights instead of more traditional and hot incandescent bulbs. This mitigates too a need for cooling that's brought on by inefficient bulbs in the first place. For instance, one large lighting structure is rated by the manufacturer at 720 watts: by simply installing more efficient bulbs, we consume ~80% less power for a similar amount of light.