Stories tagged solar thermal


The new solar thermal array: And, yes, this was the largest photo I could find on short notice.
The new solar thermal array: And, yes, this was the largest photo I could find on short notice.Courtesy US Department of Energy
A couple of months ago, I noticed something happening on the roof of the RiverCentre, the big building across the street from the Science Museum. After noticing, however, I didn’t give it any more thought. This was for two reasons: because a couple of months ago it was approximately one billion degrees below zero here, and I didn’t want to stand outside looking at roofs any longer than I had to; and because I’m a firm believer that you shouldn’t stare too long at anything you aren’t certain about. Don’t believe me? Examples: the sun (it’ll burn your eyes), chimpanzees (they will literally tear you to pieces), and roadkill (it’s gross).

At any rate, it turned out that the goings-on on the RiverCentre roof would have been largely harmless to watch, and that they were a part of a big, interesting project that I hadn’t heard about—they were installing a large array of solar thermal panels.

Solar thermal panels, just as a reminder, aren’t exactly like the photovoltaic solar panels you might be thinking of. Unlike panels that use sunlight to produce electricity, solar thermal panels absorb the heat in sunlight (or solar radiation, if the distinction bugs you), and uses it to heat water.

So … the new solar array on the RiverCentre is a joint project between the RiverCentre itself, and St. Paul District Energy, another neighbor of the Science Museum, which supplies hot and cold water to buildings downtown for efficient heating and cooling. The array has 144 solar panels, altogether taking up about the area of half a football field, and they should be able to produce about 1 megawatt of power.

Now, compared to a 1,000-megawatt coal or nuclear power station, 1 measly megawatt probably doesn’t seem like much, but it’s nothing to sneeze at. A single megawatt is still approximately enough to power 1,000 homes. Sort of.

It depends on the average consumption of the homes in the area, which varies from region to region, but 1 megawatt is usually touted as the power consumed by 1000 homes. And, in any case, this is a little different, because it’s not feeding an electrical power grid, but a grid of heat energy for downtown—any extra heat that’s not used by the RiverCentre facilities will be fed back to District Energy, which will redistribute it around the city.

The new array is the largest of its kind in the Midwest, and, in addition to creating a local energy source (as opposed to buy coal or natural gas from somewhere else), it should reduce St. Paul’s carbon dioxide emissions by about 900,000 pounds annually—more or less the amount created by 90 vehicles in a year.

Again, 90 cars’ worth of CO2 may not seem like much, but it’s a start, and it’s kind of cool that that’s just from the panels on one building. And, with the help of a million and a half dollar stimulus from the Minnesota Office of Energy Security, a mix of solar thermal and photovoltaic solar panels are going to be installed on 10 more buildings along the Central Corridor. In addition to the new light rail line from St. Paul to Minneapolis, the Central Corridor is meant to be a showcase for a bunch of energy innovation projects. (Click that last link for a list of projects—there are a whole bunch.)

Pretty slick. (More info and links here.)

This kid is contributing to alternative energy development: In his own way.
This kid is contributing to alternative energy development: In his own way.Courtesy jellywatson
I guess that the guy who invented the Super Soaker squirt gun is also kind of an all-around engineering genius. His company is currently developing a new kind of solar panel that converts heat (instead of light) into electricity. It could be a really big deal, or it could be slightly misplaced enthusiasm (see the "Bloom Box".)

In any case, read about it here. It's sort of exciting technology, and the inventor, Lonnie Johnson, has an interesting story.


What is the best way to store solar energy?

Solar Two: Heat from the sun is stored in a tower containing molten salt.
Solar Two: Heat from the sun is stored in a tower containing molten salt.Courtesy United States Department of Energy
What is a good way to store solar energy for when the sun doesn't shine? Batteries are expensive and wear out. Instead of storing electricity, solar thermal systems store heat. A coffee thermos and a laptop computer’s battery store about the same amount of energy. The thermos costs about $5 and the laptop battery $150.

Molten salt at 1000+ degrees

By reflecting sunlight at a tall "power tower", tens of thousands of gallons of molten salt can be heated to very high temperatures (1000 degrees F). The heated salt is used to boil water into steam, spin a turbine and make electric power. By regulating the release of heat, generators can continue to run on rainy days and during the night.

"This technology has been successfully demonstrated and is ready for commercialization. From 1994 to 1999, the Solar Two project demonstrated the ability of solar molten salt technology to provide long-term, cost effective thermal energy storage for electricity generation."

SolarReserve will build solar thermal electric plants

SolarReserve, a company backed in part by United Technologies, is using funding from a U.S. Department of Energy grant to develop utility-scale solar thermal electric generating plants between 100-600 megawatts of electricity. One megawatt is enough power to supply approximately 1,000 US households. Read more at SolarReserves FAQ webpage.

New York Times
SolarReserve website (includes a video)