• Tuesday, September 01st, 2009
ZEH Overview
Imagine a home that is not only energy efficient, but also produces its own power. Just like a typical home, a Zero Energy Home (ZEH) is connected to, and uses energy from, the local electric utility. But unlike typical homes, at times the ZEH makes enough power to send some back to the utility company. Annually, a ZEH produces enough energy to offset the amount purchased from the utility provider, resulting in net-zero annual energy bills.
A ZEH combines state-of-the-art, energy-efficient construction techniques and equipment with renewable energy systems to return as much energy as it takes on an annual basis. When renewable resources cannot provide the entire home’s power (at night or on a cloudy winter day) the homeowner purchases energy from the utility provider. When renewable resources produce more than the house is using (during sunny days when no one is home) power is sent back into the utility grid. In some cases, the utility provider will operate the home’s electric meter in reverse, essentially providing the homeowner with full retail value for their energy.
Why Build a Zero Energy Home?
One of the major issues we are faced with today is global warming, which is negatively affecting the environment and weather patterns worldwide. Global warming is a direct result of harmful gas which is being emitted into the earth’s atmosphere. Zero Energy Homes do not consume energy, and therefore do not produce pollution or emissions which help to reduce global warming.
Is Zero Energy Home Realistic?
Once just a concept, Zero Energy Homes are now a reality throughout all the world. The opportunities to construct ZEHs are growing as solar and other renewable energy technologies become more affordable. Never having to pay energy bills is a very attractive concept, however, only if achieving this high level of performance does not greatly increase building costs.
By following the two simple steps below, a ZEH can be built without adding considerable costs.
- Design the house to minimize energy consumption. By combining the several modern techniques highlighted below energy consumption can be reduced by approximately 70-80%.
- Use a renewable source of energy to supply the remaining 20-30% of energy which regularly built home would consume. Either solar panels or wind mills can be used for that.
Please, share your ideas about your green harmony home!
• Thursday, June 10th, 2010
One of the most frequent objections to renewable energy systems is that their production is too variable. But technologies continue to be developed that will allow storage of power generated from wind, solar, and other intermittent renewable sources. The latest development comes from researchers at Isentropic in Cambridge, England who propose giant batteries filled with gravel and argon gas. These batteries would provide a number advantages over pumped hydro, which is presently used for almost all electricity storage today, as well as over underground compressed air storage.
The gravel battery system would use excess capacity generated by a renewable source to heat and pressurize the argon gas and then pump it through a gravel filled silo to store energy. Then, when demand calls for electricity, the system is simply operated in reverse to generate electricity. According to the company, the system’s “round trip efficiency is over 72% – 80%.” This is comparable to the efficiency of pumped storage hydro, which has an efficiency of 70% – 85%. But gravel batteries are much more compact, and can be more readily installed in relatively flat areas characteristic of many areas with good windpower potential, such as the American Great Plains. A gravel battery can use far less land (1/300th) than that required for a pumped hydro lake, as well.
Underground compressed air storage is another technology that has been suggested, but that requires the presence of underground caverns, which are not always present where you might want to put a power storage facility. In addition to being able to be located anywhere, gravel batteries could be relatively inexpensive because they do not need costly materials. Costs could be as low as $55/kWh, and $10/kWh at scale for large installations.
Credit to: Philip Proefrock
• Tuesday, July 13th, 2010
Minesto, a spin-off from Swedish automaker Saab, is developing what it calls it’s “Deep Green” technology”, underwater kites tethered to the ocean floor that could produce continuous energy from tidal flows. A single Deep Green turbine could produce up to 500 kilowatts of electricity. And tides are much more regular than winds, so that the energy produced would be less erratic and variable.
The kites have a 12m (almost 40 ft) wingspan. The kites would remain at least 20m (66 feet) below the surface, to prevent conflicts with ocean navigation and minimize visual impact. Tidal flow as low as 1.6 meters/second can be used to create the lift necessary to move the kite.
Since the underwater kite is anchored to the ocean floor, it is able to move at much faster speeds, which makes the turbine more effective, as it traverses back and forth in order to generate electricity. Although wind-based deepwater offshore power systems are difficult to install and operate, Deep Green tidal kites would be well suited for installation in deeper waters. Furthermore, the underwater kites are much lighter and easier to install than the equipment needed for other deepwater generation systems. Deepwater generating systems have the additional expense and technical hurdles of transmitting the power over a greater distance. But the higher efficiency and more consistent generation offered by Deep Green could offset those drawbacks.
The company indicates the Deep Green system offers an operating cost of 0.06-0.14 Euros/kWh, as compared to 0.15-0.30 Euros/kWh for other tidal systems, and 0.10-0.12 Euros/kWh for offshore wind systems.
A scale model of Deep Green will be tested in Northern Ireland next year as the next stage of development for this system.
Credit to: http://green.yahoo.com/
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