Wave Power Lights Up U.S. Electrical Grid For First Time

by Ariel Schwartz

We write a lot about wave power here at Inhabitat, but functional wave farms are few and far between. Now Ocean Power Technologies has hooked up its PB40 PowerBuoy to the grid at the Marine Corps Base in Hawaii, marking the first time waves have provided energy to the U.S. electrical grid.

 

Unlike many tidal power devices, the PowerBuoy generates energy from the rising and falling of the waves. A 10 MW PowerBuoy station occupies 12.5 hectares of ocean.
The Hawaii-based PowerBuoy was first deployed three-quarters of a mile off the Oahu coast in December 2009. With the new Marine Corps hookup, OPT hopes to prove that the PowerBuoy can produce utility-grade renewable energy. If all goes well with the Marine Corps station, we can expect more wave power to hit the U.S. soon — OPT already signed a stakeholder agreement for a utility-scale wave energy project in Oregon.

Liquid Energy: New Microbe Tech Turns Sun and CO2 Into Fuel

by Timon Singh

Biofuel startup Joule Unlimited has announced that it has engineered microbes that require only sunlight and CO2 to produce ethanol, diesel, or other hydrocarbons. The company formally announced that it has obtained a patent for a genetically modified version of cyanobacteria that converts carbon dioxide, dirty water and sunlight into a liquid hydrocarbon that is functionally equivalent to regular diesel.

According to the patent, the engineered cyanobacteria contains “a recombinant acyl ACP reductase (AAR) enzyme and a recombinant alkanal decarboxylative monooxygenase (ADM) enzyme.”   What this concoction of cyanobacteria and enzymes does is allow for hydrocarbon production in a single step, converting captured sunlight into ‘liquid energy’, that can be either ethanol or diesel.

“This patent award represents a critical milestone for our IP strategy and validates the truly revolutionary nature of our process, which has the potential to yield infrastructure-compatible replacements for fossil fuels at meaningful scale and highly-competitive costs, even before subsidies,” said Bill Sims, President and CEO, Joule. “Our vision since inception has been to overcome the limitations of biomass-based technologies, from feedstock costs and logistics to inefficient, energy-intensive processing. The result is the world’s first platform for converting sunlight and waste CO₂ directly into diesel, requiring no costly intermediates, no use of agricultural land or fresh water, and no downstream processing.”
Formerly known as Joule Biotechnologies, the company, which is based in Cambridge, Massachusetts, announced late last year that it had developed technology which could produce the equivalent of 25,000 gallons of ethanol per acre per year and 15,000 gallons of diesel per acre per year of drop-in hydrocarbon fuels, using only sunlight, CO₂ and  water as inputs. The Solar Converter along with the new bacteria and a technology known as helioculture is the basis of this claim. Pilot production on diesel begins later this year.
While the project is still in its pilot testing phase, it’s already producing 10,000 gallons of ethanol a year, or 40 percent of its goal, on its pilot lines in Leander, Texas. It is expected that production will begin by the end of the year with commercial production commencing in 2012.  If it is successful, not only could it mean cheap biofuel (selling at $30 a barrel, compared to $70 for oil), but it could mean a fully sustainable form of fuel that doesn’t need food crops to create it. Fuel could literally be created out of thin air!

New solar energy conversion process could revamp solar power production

New solar energy conversion process could revamp solar power production

A small PETE device made with cesium-coated gallium nitride glows while being tested inside an ultra-high vacuum chamber. The tests proved that the process simultaneously converted light and heat energy into electrical current. Credit: Photo courtesy of Nick Melosh, Stanford University

Stanford engineers have figured out how to simultaneously use the light and heat of the sun to generate electricity in a way that could make solar power production more than twice as efficient as existing methods and potentially cheap enough to compete with oil.

Unlike photovoltaic technology currently used in solar panels - which becomes less efficient as the temperature rises - the new process excels at higher temperatures.

Called 'photon enhanced thermionic emission,' or PETE, the process promises to surpass the efficiency of existing photovoltaic and thermal conversion technologies.
"This is really a conceptual breakthrough, a new energy conversion process, not just a new material or a slightly different tweak," said Nick Melosh, an assistant professor of materials science and engineering, who led the research group. "It is actually something fundamentally different about how you can harvest energy."
And the materials needed to build a device to make the process work are cheap and easily available, meaning the power that comes from it will be affordable.
Melosh is an assistant professor of materials science and engineering, and is senior author of a paper describing the tests the researchers conducted. It was published online August 1, in Nature Materials.
"Just demonstrating that the process worked was a big deal," Melosh said. "And we showed this physical mechanism does exist, it works as advertised."
Most photovoltaic cells, such as those used in rooftop solar panels, use the semiconducting material silicon to convert the energy from photons of light to electricity. But the cells can only use a portion of the light spectrum, with the rest just generating heat.
This heat from unused sunlight and inefficiencies in the cells themselves account for a loss of more than 50 percent of the initial solar energy reaching the cell.
If this wasted heat energy could somehow be harvested, solar cells could be much more efficient. The problem has been that high temperatures are necessary to power heat-based conversion systems, yet solar cell efficiency rapidly decreases at higher temperatures.
Until now, no one had come up with a way to wed thermal and solar cell conversion technologies.
Melosh's group figured out that by coating a piece of semiconducting material with a thin layer of the metal cesium, it made the material able to use both light and heat to generate electricity.
"What we've demonstrated is a new physical process that is not based on standard photovoltaic mechanisms, but can give you a photovoltaic-like response at very high temperatures," Melosh said. "In fact, it works better at higher temperatures. The higher the better."
While most silicon solar cells have been rendered inert by the time the temperature reaches 100 degrees Celsius, the PETE device doesn't hit peak efficiency until it is well over 200 degrees C.
Because PETE performs best at temperatures well in excess of what a rooftop solar panel would reach, the devices will work best in solar concentrators such as parabolic dishes, which can get as hot as 800 degrees C. Dishes are used in large solar farms similar to those proposed for the Mojave Desert in southern California and usually include a thermal conversion mechanism as part of their design, which offers another opportunity for PETE to help generate electricity, as well as minimizing costs by meshing with existing technology.
"The light would come in and hit our PETE device first, where we would take advantage of both the incident light and the heat that it produces, and then we would dump the waste heat to their existing thermal conversion systems," Melosh said. "So the PETE process has two really big benefits in energy production over normal technology."
Photovoltaic systems never get hot enough for their waste heat to be useful in thermal energy conversion, but the high temperatures at which PETE performs are perfect for generating usable high temperature waste heat. Melosh calculates the PETE process can get to 50 percent efficiency or more under solar concentration, but if combined with a thermal conversion cycle, could reach 55 or even 60 percent - almost triple the efficiency of existing systems.
The team would like to design the devices so they could be easily bolted on to existing systems, making conversion relatively inexpensive.
The researchers used a gallium nitride semiconductor in the 'proof of concept' tests. The efficiency they achieved in their testing was well below what they have calculated PETE's potential efficiency to be, which they had anticipated. But they used gallium nitride because it was the only material that had shown indications of being able to withstand the high temperature range they were interested in and still have the PETE process occur.
With the right material - most likely a semiconductor such as gallium arsenide, which is used in a host of common household electronics - the actual efficiency of the process could reach up to the 50 or 60 percent the researchers have calculated. They are already exploring other materials that might work.
Another advantage of the PETE system is that by using it in solar concentrators, the amount of semiconductor material needed for a device is quite small.
"For each device, we are figuring something like a six-inch wafer of actual material is all that is needed," Melosh said. "So the material cost in this is not really an issue for us, unlike the way it is for large solar panels of silicon."
The cost of materials has been one of the limiting factors in the development of the solar power industry, so reducing the amount of investment capital needed to build a solar farm is a big advance.
"The PETE process could really give the feasibility of solar power a big boost," Melosh said. "Even if we don't achieve perfect efficiency, let's say we give a 10 percent boost to the efficiency of solar conversion, going from 20 percent efficiency to 30 percent, that is still a 50 percent increase overall."
And that is still a big enough increase that it could make solar energy competitive with oil.
Provided by Stanford University

Stanford Unveils Solar Tech That Harnesses Light and Heat

by Cameron Scott

Photo by Nick Melosh
We currently have two types of solar energy: energy generated from light, using silicon-based photovoltaic cells, and energy generated from heat, using solar concentrators and heat-conversion systems. What if we could collect both types of energy at once? Stanford researchers recently unveiled a new solar tech that can do exactly that — their PETE devices utilize a semiconducting material coated with cesium to boost efficiency levels up to 60 percent — three times that of existing systems.

Rooftop solar panels use silicon to convert light into electricity. But their efficiency declines rapidly at higher temperatures (like those needed to power heat-conversion systems). An either/or choice presents itself — but Stanford researchers found that a cesium coating allowed semiconducting materials to convert both light and heat into energy.
They dubbed the process PETE, for photon enhanced thermionic emission. Best of all, PETE devices could be cheaply and easily incorporated into existing solar collection systems. (Because the system hits peak efficiency at over 200 degrees Celsius, it’s not a good fit for rooftop arrays.) “The light would come in and hit our PETE device first,” explained lead researcher Nick Melosh. “We would take advantage of both the incident light and the heat that it produces, and then we would dump the waste heat to existing thermal conversion systems.”
PETE devices require only a small amount of semiconducting material, making them cheap. Melosh’s team also hopes to design devices that can easily be bolted on to existing solar collection systems, so that conversion would also be low-cost.
When used with the heat-conversion process, PETE devices could reach 60 percent efficiency. But even if they boost efficiency just to 30 percent, they will bring solar power down to the price point of oil. And that’s a good thing.

 

“Wind Lens” Turbines Could Boost Energy Generation 3X

by Ariel Schwartz

Forget about traditional tri-blade wind turbines — the ultra-efficient turbine of the future might look completely different if Kyushu University professor Yuji Ohya has anything to say about it. Ohya and his team recently unveiled the Wind Lens, a honeycomb-like structure that purportedly triples the amount of wind energy that can be produced by offshore turbines.

The Wind Lens was unveiled at this month’s Yokohama Renewable Energy International Exhibition 2010. The structure works similarly to a magnifying glass that intensifies light from the sun — except in this case, the lens intensifies wind flow. Ohya’s design doesn’t have too many moving parts — just a hoop (AKA a brimmed diffuser) that “magnifies” wind power, and a turbine that is rotated by wind captured from the hoop. Each Lens, which measures 112 meters in diameter, can provide enough energy for an average household.
Ohya doesn’t know if the Lens will go into commercial production, but if nothing else, it could provide a more aesthetically appealing alternative to traditional offshore turbines.

 

Solar Power Is Cheaper Than Nuclear for the First Time

by Cameron Scott

Here’s bright spot in the news of the day: energy from new solar installations has, for the first time, become cheaper than energy from new nuclear plants, according to a new Duke University study. Thanks to cost-saving technologies and economies of scale, price can no longer be an excuse to invest in nuclear power rather than solar.

In North Carolina, nuclear energy costs 16 cents per kilowatt hour (the energy required to run 10 100-watt light bulbs for an hour), whereas solar is now going for 14 cents per kWh — a rate that continues to fall. In regions with more annual sunlight, the price gap is almost certainly even more pronounced. The data also analyzed only conventional photovoltaic power, not the concentrating technologies of troughs and reflectors, which also bring costs down.
The study was developed in response to aggressive lobbying by the nuclear industry, which has tried to position itself as the most affordable way to reduce carbon emissions. The study factors in governmental subsidies for both power sources, but found that even if all subsidies were removed, solar power would still be cheaper within a decade.

NY’s Solar Thermal Plan Will Save State $175 Million Annually

by Brit Liggett

Sixty percent of the energy used in buildings in New York State goes to heat and hot water. This power heavy fact has been the the driving force behind a newly devised solar thermal energy plan that could eventually save New York State residents $175 million a year. Given that the last nation-wide energy bill was tossed out the window, individual states are now coming under pressure to come up with their own energy saving tactics. Thankfully, even in the face of ailing government support, New York’s new solar thermal plan is a shining example of how sustainable living remains a primary cause for most individuals. The state’s forward thinking plan will call for up to 1 million new solar thermal systems placed statewide, together able to provide a total of 2,000 MWth of solar powered heat by 2020.

Solar thermal energy harnesses the power of the sun to make hot water and feed steam heating systems. Much of the heat in older buildings comes from steam heat, so officials see solar thermal as a great alternative to feeding these systems. Relative to places like Germany where the solar thermal industry is booming — they install about 200,000 solar thermal heaters per year — the US has failed to see the value of such technology, often only perceiving it as useful in low-energy contexts such as for the heating of swimming pools. However, it is estimated that solar thermal heaters have the capacity to generate 50% of the hot water needed across the US.
Understanding the gains to be had with this innovative, yet simple and easily implemented technology, New York State will kick off a program which should provide incentives, educational opportunities, permitting improvements, research and development and installer training programs to encourage the installation of solar thermal systems. The program is expected to decrease energy for heating use by 6 million US gallons of oil, 9.5 million ft³ of natural gas and displace 320 GWh of electricity production per annum. With 70% of the systems coming from residential buildings and 30% of the systems from commercial buildings, the state estimates there will be a whopping $175 million in energy savings annually.

 

World’s First Molten Salt Solar Plant Produces Power at Night

by Philip Proefrock

Sicily has just announced the opening of the world’s first concentrated solar power (CSP) facility that uses molten salt as a heat collection medium. Since molten salt is able to reach very high temperatures (over 1000 degrees Fahrenheit) and can hold more heat than the synthetic oil used in other CSP plants, the plant is able to continue to produce electricity even after the sun has gone down.

While photovoltaic solar panels work by directly producing electricity from sunlight, CSP plants use mirrors to concentrate sunlight and produce high temperatures in order to drive a turbine to generate electricity. CSP plants have been in existence for many years, but the Archimede plant is the first instance of a facility that uses molten salt as the collection medium.
Heat from the molten salt is used to boil water and drive the turbines, just like other fossil fuel plants. CSP plants use the same kind of steam turbines as typical fossil fueled power plants. This makes it possible to supplement existing power plants with CSP or even to retrofit plants to change over to clean energy producing technology. Some existing CSP plants have used molten salt storage in order to extend their operation, but the collectors have relied on oil as the heat collection medium. This has necessitated two heat transfer systems (one for oil-to-molten-salt, and the other for molten-salt-to-steam) which increases the complexity and decreases the efficiency of the system. The salts used in the system are also environmentally benign, unlike the synthetic oils used in other CSP systems.

Since molten salts solidify at around 425 degrees F, the system needs to maintain sufficient heat to keep from seizing up during periods of reduced sunlight. The receiver tubes in the Archimede facility are designed to maximize energy collection and minimize emissions with a vacuum casing that enables the system to work at very high temperatures required with molten salts. By using the higher temperatures of molten salts, instead of oil, which has been used in other CSP plants until this point, the plant is able to maintain capacity well after the sun sets, allowing it to continue generating power through the night.
The Archimede plant has a capacity of 5 megawatts with a field of 30,000 square meters of mirrors and more than 3 miles of heat collecting piping for the molten salt. The cost for this initial plant was around 60 million Euros.

“Smart” Metal to Make Air-Conditioning 175% More Efficient

by Ariel Schwartz

You know the drill: the temperature shoots up, the central air-conditioning goes on full-blast, and your electric bill climbs into the stratosphere. A new “smart” metal developed by researchers at the University of Maryland could change all that by increasing the efficiency and reducing the emissions of air-conditioning and refrigeration systems by up to 175%.

The “thermally elastic” alloy, which is supported by a $500,000 grant from the US Department of Energy, works like a traditional compressor-based system, but uses far less energy. The University of Maryland team explains, “The approach is expected to increase cooling efficiency 175 percent, reduce U.S. carbon dioxide emissions by 250 million metric tons per year, and replace liquid refrigerants that can cause environmental degradation in their own right.”
There is still plenty of work to be done before smart metals can be deployed. Prototype testing begins soon, and after that, there is a long road to commercial production. But considering that air-conditioning systems represent the largest portion of home electric bills during the summer, the sooner this technology is released, the better.

Micro Fuel to power your house

Oorja Unveils Micro Fuel Cell That Could Power Your House

by Ariel Schwartz

Were you impressed by the recently unveiled Bloom Energy “micro power plant”? Well the stationary fuel cell already some competition in the form of a methanol fuel cell device from a California-based startup called Oorja Protonics. Oorja’s soon-to-be-unveiled device is much cheaper and can generate 5 kw of energy — enough to power a home or small business.
The small device isn’t quite as powerful as Bloom Energy’s fuel cell — 20 Oorja devices could provide the same power as a single Bloom Energy Server. But while Bloom’s device costs between $700,000 and $800,000, Oorja’s fuel cell will cost less than $15,000, making it much more accessible to the home market. Another advantage: Bloom’s fuel cell provides minimal heat, while Oorja’s device generates both heat and power.
Of course, it’s slightly unfair to directly compare the two. Bloom’s fuel cell runs on a number of fuels, including methane and biogas. Oorja’s device, in comparison, runs on methanol. We’ll find out soon what potential buyers prefer — Oorja’s fuel cell will be released in a few months.

Ultra-Efficient Bladeless Wind Turbine Inspired by Nikolai Tesla

by Philip Proefrock

SolarAero recently unveiled a new bladeless wind turbine that offers several advantages over current wind turbines — it emits hardly any noise in operation, has few moving parts, and since it doesn’t use spinning blades it’s much less of a hazard to bats and birds. The whole assembly is inside an enclosed housing, with screened inlets and outlets to keep animals safely out. It also can be installed on sensitive locations such as radar installations or sites under surveillance where the rotating blades cause detrimental effects. Read on to learn what makes it work.

 

 

 

Whether they are vertical axis or horizontal axis, typical wind turbines work by catching moving air with blades, and using that force to rotate the axle, which turns a generator to produce electricity. Instead of pushing on blades, SolarAero’s turbine is based on the Tesla turbine originally developed by Nikolai Tesla. The principle of the Tesla turbine is to set up an array of closely-spaced, very thin, and extremely smooth metal disks. The viscous flow of air moving in parallel to the disks is what propels the turbine, instead of buffeting blades with moving air. This makes for a more compact mechanism with only one moving part: the turbine-driveshaft assembly.
According to the company, this turbine should cost around $1.50 per watt of rated output, and have a lifetime operating cost of about 12 cents per kilowatt-hour — comparable to, or even better than, current retail electrical rates in many parts of the country. This would make the SolarAero turbine about 2/3 the price of a comparable bladed unit, and because of the significantly lower operating costs, lifetime maintenance could be just 1/4 the cost. At this point the project is still under development, and no manufacturer has been lined up as of yet.

Turbine Light Illuminates Highways With Wind

by Ariel Schwartz

As more and more people across the world adopt cars as their primary mode of transportation, well-lit highways become increasingly important. But how can we sustainably power all those energy-sucking lights? TAK Studio addressed that question in their entry into this year’s Greener Gadgets competition to find the green technology solution of the future. Dubbed the Turbine Light, their design aims to illuminate our roadways using the power of the wind.

TAK’s wind-powered light uses the moving air from cars zipping by on the highway to generate energy that can be used to power roadside lighting. It’s a controversial idea–could wind from passing cars actually provide enough power for lighting?–but one that has the potential to save lots of cash in already wind-heavy regions. Alternatively, cities might consider using solar-powered lights instead. The idea has been proven to work many times over, including at the recent COP15 climate change conference.

Researchers Develop First Paper Supercapacitor

by Ariel Schwartz

In the near future, we might have electronic devices made entirely out of paper–with paper displays, paper transistors, and even paper supercapacitors. Researchers at Stanford University have developed the first paper supercapacitor by printing carbon nanotubes onto paper. Similar paper supercapacitors can be printed on everything from grocery ads to Xerox paper.

Stanford researchers developed the supercapacitor by coating both sides of a piece of paper with polyvinylidene fluoride (PVDF), causing it to function as an electrolyte separator and membrane. The treated paper allows the supercapacitor, made entirely out of single walled carbon nanotubes (SWNTs), to bond to the paper — much like ink from a pen bonds to paper. It works well, too — the device loses minimal capacitance after 2500 charge-discharge cycles.
Most importantly, the development of paper supercapacitors could usher in an era where we can simply toss small electronic devices in the recycling bin when we’re done with them–no need to hunt for electronics recycling centers. Because the easier it is to recycle, the less likely it is that electronics will end up in our landfills.

GEOTHERMAL or GROUND SOURCE HEAT PUMPS

CONSUMER ENERGY CENTER on GEOTHERMAL or GROUND SOURCE HEAT PUMPS

Heat pumps move heat from one place to another - from outside to inside a home, for example. That's why they're called "heat pumps."
We explained the way that they work in the section "Central HVAC." Here's a simplified version of how a heat pump works:
All heat pumps have an outdoor unit (called a condenser) and an indoor unit (an evaporator coil).
A substance called a refrigerant carries the heat from one area to another. When compressed, it is a high temperature, high-pressure liquid. If it is allowed to expand, it turns into a low temperature, low pressure gas. The gas then absorbs heat.
In the winter the normal heat pump system extracts heat from outdoor air and transfers it inside where it is circulated through your home's ductwork by a fan.
Even cold air contains a great deal of heat; the temperature at which air no longer carries any heat is well below -200 degrees Fahrenheit. But the coldest temperature ever recorded in the lower 48 states was -70 degrees, recorded at Roger Pass, Montana on January 20, 1954. Obviously in such weather, a heat pump would have to work pretty hard to produce 68-degree temperatures inside your home.
That's why geothermal heat pumps are so efficient.
Geothermal heat pumps are similar to ordinary heat pumps, but instead of using heat found in outside air, they rely on the stable, even heat of the earth to provide heating, air conditioning and, in most cases, hot water.
From Montana's minus 70 degree temperature, to the highest temperature ever recorded in the U.S. - 134 degrees in Death Valley, California, in 1913 - many parts of the country experience seasonal temperature extremes. A few feet below the earth's surface, however, the ground remains at a relatively constant temperature. Although the temperatures vary according to latitude, at six feet underground, temperatures range from 45 degrees to 75 degrees Fahrenheit.
Ever been inside a cave in the summer? The air underground is a constant, cooler temperature than the air outside. During the winter, that same constant cave temperature is warmer than the air outside.
That's the principle behind geothermal heat pumps. In the winter, they move the heat from the earth into your house. In the summer, they pull the heat from your home and discharge it into the ground.
Studies show that approximately 70 percent of the energy used in a geothermal heat pump system is renewable energy from the ground. The earth's constant temperature is what makes geothermal heat pumps one of the most efficient, comfortable, and quiet heating and cooling technologies available today. While they may be more costly to install initially than regular heat pumps, they can produce markedly lower energy bills - 30 percent to 40 percent lower, according to estimates from the U.S. Environmental Protection Agency, who now includes geothermal heat pumps in the types of products rated in the EnergyStar® program. Because they are mechanically simple and outside parts of the system are below ground and protected from the weather, maintenance costs are often lower as well.
As an added benefit, systems can be equipped with a device called a "desuperheater" can heat household water, which circulates into the regular water heater tank. In the summer, heat that is taken from the house and would be expelled into the loop is used to heat the water for free. In the winter, the desuperheater can reduce water-heating costs by about half, while a conventional water heater meets the rest of the household's needs. In the spring and fall when temperatures are mild and the heat pump may not be operating at all, the regular water heater provides hot water.
How Do They Compare?
Surveys taken by utilities have found that homeowners using geothermal heat pumps rate them highly when compared to conventional systems. Figures indicate that more than 95 percent of all geothermal heat pump owners would recommend a similar system to their friends and family. 

Cost
As a rule of thumb, a geothermal heat pump system costs about $2,500 per ton of capacity. The typically sized home would use a three-ton unit costing roughly $7,500. That initial cost is nearly twice the price of a regular heat pump system that would probably cost about $4,000, with air conditioning.
You will have to, however, add the cost of drilling to this total amount. The final cost will depend on whether your system will drill vertically deep underground or will put the loops in a horizontal fashion a shorter distance below ground. The cost of drilling can run anywhere from $10,000 to $30,000, or more depending on the terrain and other local factors.
Added to an already built home an replacing an existing HVAC unit, an efficient geothermal system saves enough on utility bills that the investment can be recouped in five to ten years. 

Durability
Geothermal heat pumps are durable and require little maintenance. They have fewer mechanical components than other systems, and most of those components are underground, sheltered from the weather. The underground piping used in the system is often guaranteed to last 25 to 50 years and is virtually worry-free. The components inside the house are small and easily accessible for maintenance. Warm and cool air are distributed through ductwork, just as in a regular forced-air system.
Since geothermal systems have no outside condensing units like air conditioners, they are quieter to operate.
How Do They Work?
Remember, a geothermal heat pump doesn't create heat by burning fuel, like a furnace does. Instead, in winter it collects the Earth's natural heat through a series of pipes, called a loop, installed below the surface of the ground or submersed in a pond or lake. Fluid circulates through the loop and carries the heat to the house. There, an electrically driven compressor and a heat exchanger concentrate the Earth's energy and release it inside the home at a higher temperature. Ductwork distributes the heat to different rooms.
In summer, the process is reversed. The underground loop draws excess heat from the house and allows it to be absorbed by the Earth. The system cools your home in the same way that a refrigerator keeps your food cool - by drawing heat from the interior, not by blowing in cold air.
The geothermal loop that is buried underground is typically made of high-density polyethylene, a tough plastic that is extraordinarily durable but which allows heat to pass through efficiently. When installers connect sections of pipe, they heat fuse the joints, making the connections stronger than the pipe itself. The fluid in the loop is water or an environmentally safe antifreeze solution that circulates through the pipes in a closed system.
Another type of geothermal system uses a loop of copper piping placed underground. When refrigerant is pumped through the loop, heat is transferred directly through the copper to the earth. 

Types of Loops
Geothermal heat pump systems are usually not do-it-yourself projects. To ensure good results, the piping should be installed by professionals who follow procedures established by the International Ground Source Heat Pump Association (IGSHPA). Designing the system also calls for professional expertise: the length of the loop depends upon a number of factors, including the type of loop configuration used; your home's heating and air conditioning load; local soil conditions and landscaping; and the severity of your climate. Larger homes requiring more heating or air conditioning generally need larger loops than smaller homes. Homes in climates where temperatures are extreme also generally require larger loops.
Here are the typical loop configurations:

Horizontal Ground Closed Loops

This type is usually the most cost effective when trenches are easy to dig and the size of the yard is adequate. Workers use trenchers or backhoes to dig the trenches three to six feet below the ground in which they lay a series of parallel plastic pipes. They backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. Fluid runs through the pipe in a closed system. A typical horizontal loop will be 400 to 600 feet long for each ton of heating and cooling.

Vertical Ground Closed Loops

This type of loop is used where there is little yard space, when surface rocks make digging impractical, or when you want to disrupt the landscape as little as possible. Vertical holes 150 to 450 feet deep - much like wells - are bored in the ground, and a single loop of pipe with a U-bend at the bottom is inserted before the hole is backfilled. Each vertical pipe is then connected to a horizontal underground pipe that carries fluid in a closed system to and from the indoor exchange unit. Vertical loops are generally more expensive to install, but require less piping than horizontal loops because the Earth's temperature is more stable farther below the surface.

Pond Closed Loops

This type of loop design may be the most economical when a home is near a body of water such as a shallow pond or lake. Fluid circulates underwater through polyethylene piping in a closed system, just as it does through ground loops. The pipes may be coiled in a slinky shape to fit more of it into a given amount of space. Since it is a closed system, it results in no adverse impacts on the aquatic system.
Although they are less applicable to California, there are other loop systems described at the Geothermal Heat Pump Consortium's Web Site. These include an Open Loop System in which ground water is pumped into and out of a building, transferring its heat in the process; and Standing Column Well Systems, which can be up to 1,500 feet deep and can also furnish potable water.
In a few places, developers have installed large community loops, which are shared by all of the homes in a housing project.
To date, geothermal heat pumps are an under-used technology, merely because few people are aware of it's potential. The Department of Energy's Office of Geothermal Technologies, however, wants to increase installations of geothermal systems to about 400,000 a year by 2005. If the goal is reached, that would mean that 2 million systems would be in service, saving consumers over $400 million per year in energy bills and reducing U.S. greenhouse gas emissions by over 1 million metric tons of carbon each year.

Are Ground Source Heat Pumps (AKA Geothermal Systems) A Good Choice?

by Lloyd Alter, Toronto

Every time I write about ground source heat pumps, (like in my post Blowing Hot and Cold on Ground Source Heat Pumps) the commenters are enraged, saying " If I were a geothermal contractor or manufacturer I would have asked that this be removed for falsely conveying what geothermal has to offer " and "engineering degree would probably help too."

But I just got my licence to practice architecture thirty years ago this month and obviously don't know what I am talking about, so it is great to find a real expert, like Alex Wilson at Green Building Advisor, saying much the same thing.

Right off the bat I am excited about his post, for he agrees with me about calling them ground source heat pumps instead of geothermal. (and if you want to see more people calling me an idiot, read the comments at Jargon Watch: Geothermal vs Ground Source Heat Pump) Alex writes:

A ground-source heat pump (GSHP) is also referred to as a "geothermal" heat pump, though I prefer the former terminology, to avoid confusion with true geothermal energy systems that rely on elevated temperatures deep underground from the Earth's mantle.

After that he could sell me on vinyl replacement windows, let alone GSHPs. Instead he goes on to point out:
They are rarely as efficient as promised; they advertise a Coefficient of Performance of 3.5 times that of straight resistance electric heating, but turn out to be around 2.5. (John Straube at Buildingscience.com notes that the COP rated efficiency may not include the energy required for the pump, suggesting that "This electrical energy can be significant, particularly if the loop is long, the pipes are small, or the flow resistance within the heat pump unit is large." That may account for the difference.)
Alex also notes that the GSHPs run on electricity, which for much of America comes from coal; if you go back to the source, efficiency the numbers are a lot lower. If you care about your carbon footprint, it is actually worse than running on natural gas.a commenter did the numbers:
1. Burn natural gas at 92% efficiency = 1.09 MMBtu of fuel which makes 130 lb CO2.
2. Burn #2 fuel oil at 83% efficiency = 1.2 MMBtu and 175 lb CO2
3. Run a ground-source heat pump and purchase 0.33 MMBtu of electricity which has made 140 lb CO2.
These numbers do not apply if you live in Quebec or parts of the Continent where you can purchase green energy from hydro or renewables.
But ultimately, Alex's objection is the same as mine: they are really expensive and there are better places to spend your money.

The reason I'm not a huge proponent of GSHPs is that they're really expensive. Most of the expense is due to the cost of digging trenches and laying tubing....It is not unusual to hear about GSHPs in Vermont costing as much as $35,000 for typical homes. For the same investment, one could spend $30,000 reducing heating loads (insulating, air sealing, replacing windows, etc.) and install a state-of-the-art mini-split heat pump.

Not only does natural gas have a lower carbon footprint than a coal-fired GSHP, but America is awash in the stuff, so much so that they are thinking of reversing the flow in the pipelines and exporting it to Canada. The development of shale gas in the States changes everything, and anyone who says that you are going to get a return on investment by switching your heating from gas to electricity is basically lying.
We need to invest in reducing our consumption, not in buying green gizmos. That is why I am so enamoured of Passivhaus design. There, the technology is simple: add a shitload of insulation and eliminate leaks. Reduce demand rather than switching supply. That is the path to energy independence and a lower carbon footprint.

Japanese Company Turns Adult Diapers into Energy Source

by Brit Liggett

Wearing adult diapers just got a whole lot cooler — a Japanese company called Super Faith has developed a miraculous system that turns used diapers into a clean fuel source in about 24 hours. The elderly care industry in Japan is growing and along with it the number of disposable adult diapers. Super Faith has figured out a way to divert the smelly waste from the landfill and use it for a cleaner cause.

 

Apparently the transformation from diaper to energy source is easy as pie. You simply place the bag of dirty diapers in the top of the machine and close it up. Once set it motion it pulverizes, sanitizes and dries the material in the diapers and then forms it into small pellets. The pellets are dry, odorless and contain 5000 kcal of heat per kilogram and are meant to be used in biomass heating and electricity systems.
Super Faith — we’re wondering if this is some sort of “lost in translation” name — has reportedly installed two SFD systems at a hospital in Tokyo’s Machida area. Each is capable of turning 700 pounds of used diapers — and everything they hold — into fuel every day. It seems the system could be used for children’s diapers as well, but Super Faith is pretty set on the adult market. With the amount of adult diapers rising each year in Japan this is a great green solution to the dirty disposal problems they are facing.