Posted on 06/10/2010 10:32:21 PM PDT by neverdem
An updated version of a two-hundred-year-old invention is turning sunlight into electricity.
Promising new solar technology to generate electricity is almost a cliche these days. Let's look at some promising old technology. Today, on Engineering Works! Listen to the podcast.
When people talk about solar energy, they usually mean one of two things. Photovoltaic panels or solar concentrating plants. Some engineers are trying something else. An updated version of a two-hundred-year-old invention to turn sunlight into electricity. This old technology is something called a Stirling engine. A Scottish clergyman named, you guessed it, Stirling, invented it in 1816.
The idea is simple. A Stirling engine has two cylinders and pistons. Kind of like a two-cylinder motorcycle engine. The space above the pistons is filled with a fluid, usually air or helium. Heat the gas in one cylinder and it expands, moving the piston. The gas cools and moves to the other cylinder, where it moves that piston and flows back to the first cylinder, where it's heated again and the whole cycle starts over. It's more complicated than this, but you should get the idea. They're a lot more efficient than conventional internal combustion engines and need only a little outside heat to keep the cycle going.
In solar power plants, sunlight provides the heat that makes the gas expand. Sunlight is focused on the Stirling engine by a concentrator that looks like a big, shiny satellite TV dish. Stirling engines spin electric generators the same way turbines or diesel engines do.
Whew! It's getting hot in here. We'll see you next time.
Engineering Works! is made possible by Texas A&M Engineering and produced by KAMU-FM in College Station.
Please don’t get me wrong. There are many places where there are hot springs and heat from the earth can be harnessed without any drilling at all. George Bush Jr. is using a geo-energy system to help heat and cool his home in Texas. Unfortunately, geoenergy is not an economical alternative to our nation’s energy needs at this time. In our state several working hydro plants that had been operating for decades have been shut down in the last few years because their permits were not renewed. Hundreds of kilowatts are no longer being produced because of non-sensical reasons that have little to do with protecting nature. I have no doubt that American ingenuity unbridled by rampant government interference would be capable of meeting our energy needs in the future.
I had relatives in Eastern Washington who lived in below grade housing because it was cooler in the summer and easier to heat in the winter. This was a common sense variation on the geothermal theme before “heat pumps”.
We are on a relatively thin continental mass where Africa has pulled away from North America and stretched the surface.
Add to that the gigantic meteor that hit the DELMARVA peninsula 35million years ago, and we have a rather broken rock access port to the upper mantle.
Assuming nothing bad happens we could literally tap virtually unlimited hot rock not otherwise associated with a volcanic fissure or mantle plume!
Without trying to give the impression that I am an expert on Stirling engines: don’t get me wrong...if someone can come up with a feasibility for warm fusion using OWB (Oprah Winfree’s Bathwater) I’m all for it. But wrt Stirlings, as you imply, highish power will require a physically large engine because the stroke has to be large and the temp differential has to be large. The examples I’ve seen indeed have the character of “demonstration” devices. All of these alternative methods, from arcane to just unusual, have their place(s): Having solar panels to charge the batts in remote highway emergency phones is fabulous. Generating power by capturing & burning methane on a pig farm is great. But these are not system-wide solutions for much of anything.
My guess is that in the absence of government interference a coal fired plant could be built for a fraction of the price and even with the price of coal factored in it would probably operate much less expensively. This is not to say that alternative energy sources shouldn't be looked into... it is just with our country's vast reserves of coal, most are not economically feasible by comparison especially when looking at large scale electrical energy energy production.
With the current level of government interference through excessive regulation and red tape in the planning and construction of power plants... we are only a few years away from sky rocketing electric rates. Many different types of energy sources might became at least temporarily economically feasible in such an environment. The problem with a shortage created by out of control government interference as is being created currently... is that investors will be leery of putting huge amounts of capital into projects that will be made obsolete when our political leadership is forced to once again apply common sense to our nations energy needs.
Already being accomplished:
http://www.stirlingenergy.com/
Oh, I agree - wholeheartedly.
I’m just injecting a little nit on the subject of Sterlings themselves. The reason why they’ve gotten a bad rap is that efficiency champions and engineers have tried to shove them into cars - and the issues in a Sterling just don’t (IMO) lend themselves to being shoved into a car or truck. They’ll be too big, too heavy, to light in torque if they’re not too big and too heavy, etc. That’s why I’m still a huge champion of diesel engines for autos and trucks.
But in a stationary installation, I think that most of the issues with a Stirling could be sufficiently solved to make them a viable alternative to PV cells in “industrial scale” solar power developments in that PV cells don’t have conversion efficiencies as high as a Stirling can get without getting to the very bleeding edge of PV cell solid state physics using some very rare minerals to dope the silicon. By my estimates, there aren’t enough rare earth minerals to salt the silicon in PV sells to get us anywhere near the power output the greenies want - there’s going to need to be some other solar->power conversion method other than PV’s.
I agree with you wholeheartedly that neither solar, nor wind, provide base-load power. They’re toys on the edge of the grid, so to speak. The calls for 20% of our power to come from “alternative” sources that aren’t base-load power... they’re silly.
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