The sun-blasted wilderness of the US Southwestern deserts may hold the key to our energy future. Stirling Energy Systems (SES) has found a way to turn all of that sunlight and heat into electricity. According to them, their system is twice as efficient as the best photovoltaic cells available.

Stirling Energy Systems builds a system that focuses the heat of the sun onto a proprietary engine that uses a closed hydrogen system to produce electricity.

Where traditional photovoltaic solar generation uses only 15% of the sun’s energy at best, the Stirling system converts 30% of that energy into electricity. The system is composed of a 37-foot diameter dish of mirrors that focus the sun’s light onto a Stirling engine.

The engine contains hydrogen which when heated expands, moving pistons, which turns a flywheel that is used to generate electricity. The hydrogen is not depleted in the process and so never needs to be replenished. The dish turns throughout the day to follow the sun. At night and on cloudy days, you need batteries.

Sandia National Labs Solar Thermal Designated User Facilities

These systems, due to their size and cost, are intended for industrial use only. Don’t expect to put one in your backyard unless you have a spare 58 square feet.

from their website:

Stirling Energy Systems holds two key patents on the solar concentrator system that were initially filed by McDonnell Douglas (by virtue of a merger, now The Boeing Company) to manufacture this solar concentrator system, as well as six of the original solar concentrator systems that were fabricated in the 1980s. SES also acquired all of the intellectual properties, including significant trade secrets regarding technical and manufacturing aspects of the solar concentrator system. SES was granted an licensing agreement with Kockums, a major Swedish defense company, to manufacture, market, and sell the Kockums 4-95 Stirling engines.

Right now a dish costs less than half a million dollars. As production ramps up, one of these units will be in the $150,000 range. A single Stirling set-up can power eight to ten American homes.

Stirling systems also have a minimal impact on the environment. They require antifreeze, lubricant, and someone with a squeegee and plenty of windex to go out there and clean off the mirrors. Actually, they use water, not windex. They might not use a squeegee.

The overall effect on the area around the dish is about the same as planting a tree. A shiny, noisy metal tree. A Stirling engine emits 66 dB of sound – just under the 70 dB at which hearing damage may start. But no smoke!

This method of generating electricity is called “solar thermal” or “concentrating solar” power. A solar thermal farm 100 miles by 100 miles could satisfy 100% of the America’s electricity needs.

BusinessWeek erroneously states that 100 square miles of dishes would satisfy US energy needs. They are not so good at math – it actually comes out to 10,000 square miles.

Is it cost effective? Hard to say. Stirling Energy Systems will not reveal the cost of generation. They do say that the dishes now cost about a quarter million each to produce. Southern California Edison (SCE) has entered a deal with Stirling to buy electricity at “well below the 11.33 cents per kWh” they are now paying for fossil-fuel generated electricity.

However, a 2003 study showed that the average cost of electricity from a Stirling dish would be 15. 37 cents per kWh. They are offsetting this cost by selling dishes.

Stirling has 20-year contracts with Southern California Edison for 500 megawatts and San Diego Gas & Electric for 300-900 megawatts.

Large view of the solar engines from above
High resolution images of the maps

sources

• BusinessWeek, September 12, 2005
• Stirling Energy
• California energy cost study (pdf)
• US DOE Energy Efficiency and Renewable Energy
• Sandia National Labs Solar Thermal Test Facility

This freeway coming up from the southeast ends in mid-air, like the freeway from The Blues Brothers. Not even Evil Knievil would attempt this leap. Coming across the Betsy Ross Bridge from New Jersey, this strange and unusual interchange was constructed to be part of the “Five-Mile-Loop,” which would have connected US 1 with 90 and 95. This would have created an “inner loop” around the downtown core of Philadelphia. It remains unbuilt.

The freeway was originally accepted and slated for completion by 1975, but rising costs and political opposition caused the Pennsylvania Department of Transportation to halt funding for all new highway projects in July of 1977. It remains as some kind of weird monument, a prefigured bridge to nowhere.

As planned, the freeway would have bisected several neighborhoods, cemeteries and parks with a tremendous concrete freeway. As it is, the roads and bridges in Pennsylvania are in a state of serious disrepair, with a total repair bill of $6.5 billion. Too much. Not going to happen.

It’s a fairly accurate estimate though. They’ve got bumper mounted lasers and downward-pointing video cameras at PennDOT, and they survey every road and bridge in Pennsylvania every two years. That’s a lot of driving– over 40,000 miles of roadway. Completely surveyed and rated. In a huge database somewhere, presumably.

Enough driving to circumnavigate the globe one and a half times over. Every two years. Full road defect information.

Not enough money to make the repairs.

All of these roads constitute areas of impervious surface, with microclimates like little deserts. The total impervious surface area (ISA) in the United States, including rooftops, parking lots, streets and roads, within the lower 48 adds up to about the size of Ohio. That’s an area greater than the amount of wetlands found in the contiguous United States.

"ISA alters the shape of stream channels, raises the water temperature, and sweeps urban debris and pollutants into aquatic environments. It also increases the frequency and magnitude of surface runoff events. These effects lead to reduced biodiversity and degradation of wetlands and riparian zones. According to the article, these effects are measurable once impervious surfaces cover 10 percent of a watershed’s surface area." Colorado NPS Connection

With 10,000 miles of new roads being constructed every year, we continue to gradually pave over the United States. More impervious surface. More roads to maintain.

Crawling along the surface of the earth in lines, like ants.

Paving the lines over, then re-paving them after each winter’s freeze-and-thaw cycle seeps through the cracks in the concrete.

This image shows the city of Philadelphia. South of the river is New Jersey. You can see how the freeway that was never built would have cut right through the city’s core, largely for the benefit of commuters in outlying regions.

As an example of urban planning gone mad consider this picture of San Francisco’s skyline from 1963. Note the giant elevated highway looping around the waterfront.

The neighborhood is still trying to recover from this concrete monstrosity, part of which was knocked down by an earthquake and then finally demolished and replaced with a commuter friendly light rail line.