December 6, 2012 – Vol.17 No. 38
HEAT DRIVES THE WORLD (MOST OF IT WE WASTE).
by Bruce Mulliken, Green Energy News
A ball of fusion energy boiling in space. So hot is our Sun that 93 million miles away it keeps our planet warm enough through its electromagnetic radiation to allow most life on Earth to thrive. That radiation – infrared radiation - heats all things it comes in contact with, which in turn transmit that solar heat to other things. Slowly, we earthlings are taking better advantage of solar heat by concentrating it with mirrors to create high temperatures to generate steam to drive turbines to make electricity. We're wasting this free resource by not utilizing it enough.
The majority of the energy we use on the planet is in the form of fuels burned for heat. The human race is not that advanced from our cave-dwelling ancestors in that regard. They began building economies around the ability to make fire and put its heat to work. Today our economies prosper by burning something. Combusting coal, natural gas, oil and biomass generates enough heat to expand gases to spin turbines to generate electricity to be fed into the power grids of the world. Even nuclear power is a thermal reaction generating high temperature, high pressure steam to generate electric power. In our land, sea and air vehicles fuel is injected into combustion chambers with air, then ignited to create hot expanding gases to push pistons or spin turbines for mechanical motive power or thrust in jet engines.
In a home, burning fuels, or with the heat of electrical resistance in metals, water or air is heated for a soothing morning shower or to warm the ambient air. On a stove top that same electrical resistance, or the burning of a fuel, generates enough heat to fry an egg, boil a pot of stew, or sizzle a steak. The kitchen's microwave oven doesn't seem like a heat device but it is. Microwaves, a version of radio waves, vibrate molecules in oils and water within foods to generate heat and cook food from the inside out.
There's a myriad of uses of heat in industry as well. Heat melts ore and scrap to make metal products and alloys. Heat melts metals to join pieces together. Heat melts sand to make glass to make the windows of your houses or the bottle for your beer. Heat bakes on the paint of your car. Heat melts plastic to make everything from shopping bags to kayaks. Heat is used in some of the most advanced manufacturing processes even those for the latest generation of airliner. Carbon fiber composite components used in Boeing's 787 Dreamliner are cured in great ovens. And, it is heat that makes the silicon crystals to be sliced into solar cells to generate electricity.
Have I made the point? Heat is what drives our global economies and industry.
Yet heat has a serious problem that's behind every energy concern and environmental degradation: Most of the heat generated for all purposes is wasted. Excess heat from about every manmade source flows into the atmosphere or our oceans, lakes and rivers This waste heat means that the most of the energy content of fuels is being spent without doing any work. The most obvious example is the internal combustion engine in most of the world's cars and trucks. These engines use only about 20 percent of the energy content in gasoline to propel the car. The rest of the energy goes out the tailpipe, out the radiator or is gobbled up as friction and heat in mechanical systems. Wasting heat means wasting fuel. It's the wasted heat that behind energy inefficiencies. If we didn't waste so much heat we wouldn't have energy and emissions problems.
The problem of wasted heat, wasted thermal energy, is being tackled with some success with new ideas and new technologies, most of which incorporate ways to capture wasted heat and put it to work.
Often the wasted heat is being productive doing related work: With cogeneration (or combined heat and power) the exhaust heat of fossil-fueled electric power generation is used to heat water for commercial, industrial or domestic purposes.
More methods are being developed and improved upon to capture waste heat and make it work improving energy efficiencies. Organic Rankine Cycle generators, using some variation of hydrocarbon gases expanded by waste heat, are running engines that in turn generate electricity convert that waste heat into useful energy. ElectraTherm's Green Machine, for instance, operating on waste heat temperatures of 77-116°C (170-240°F) can provide up to 65 kilowatts of electricity: All from heat that was once thrown away.
Cool Energy's SolarHeart Stirling engine can use waste heat from a variety of sources to generate electricity improving overall system energy efficiency.
Elsewhere in the heat-to-energy world, Combinations of some metal alloys emit free flowing electrons - electricity - when heated. Already thermoelectric generators are being tested for use in cars to turn the heat energy in hot exhaust gases into electricity There's room for considerable improvement and adaptation in this technology.
Given the wide scope of the wasted heat energy problem, there's always room for new technologies as well. One of these is a rekindling of a nearly two century old heat engine, the Stirling engine. Devised by Scottish preacher Robert Stirling as a safer alternative to steam engines of the early 19th century, the Stirling external heat engine has a kind of mystique attached to it. Many followers watch modern day Stirling engines be developed only to fade away and come back again in yet a new variation.
Being a heat engine, and one friendly to external sources of heat (like waste heat), the Stirling engine seems poised to join the group of technologies tapped to tackle the waste heat/waste energy problem.
SolarHeart Stirling engine technology is running off exhaust heat from a 30 kW diesel generator
One upstart Stirling engine company is setting its sights on the waste heat market: Cool Energy, of Boulder, Colorado which is developing it's SolarHeart engine. Cool Energy is adapting the engine for a wide variety of fairly low temperature heat sources including solar heat, waste heat from engines and waste heat from a wide variety of commercial, industrial and military sources. Waste heat from roasting ovens in the processed food industry could be turned into electricity with the SolarHeart engine. Heat emanating from industrial processes (like those ovens curing airplane parts) could be turned into useable electricity. In the military, a SolarHeart engine aboard ship, for instance, could capture the waste heat in exhaust to lower fuel consumption reducing the need and cost of refueling. The SolarHeart engine operates at about 22 percent thermal to electric efficiency.
Cool Energy, has been testing one of its 3 kW engines in a program with engineers at CEA/Grenoble - France's equivalent to the U.S. National Renewable Energy Laboratory (NREL). The successful test brings the SolarHeart technology one step closer to deployment. Global electric component provider Schneider Electric has been considering SolarHeart in a program to bring power to villages without electricity in developing nations. In Boulder, Colorado, Cool Energy is currently demonstrating the capture of exhaust heat from diesel-powered electrical generators to boost their electricity output, improving the fuel efficiencies of the generators.
Unlike some energy technologies, Stirling engines, like SolarHeart, are manufactured with common materials and time-tested processes. Together, these will keep costs low.
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