Water heating can be responsible for nearly 20% of a home's energy usage. Directly heating water with the sun's energy is far more efficient than making electricity with solar panels and then using electricity to heat the water. But the appearance of rooftop water heating panels can be a drawback for some homeowners. A new option is the Greenward ridge vent from Energy Alternatives, which uses the entire roof as a heat collector (something that your roof is already doing).

The idea of using the roof as a solar heat collector is not a new one. But the way Greenward does it makes it far easier to install and still get a significant benefit. Instead of having to thread tubes back and forth throughout the entire roof, the Greenward tubes are installed just at the ridge, which should be the warmest part of the roof due to the natural ventilation.

Since the Greenward ridge vent is like other ridge vents, where the final exterior appearance depends on using the same shingles as the rest of the roof, it isn't limited to a particular look. And, because the Greenward ridge vent is only installed along the ridge of the roof, it makes it an easy candidate for retrofit installations on existing homes.

Heated water from the ridge goes through a heat exchanger to store hot water in a tank. It can then be drawn directly into the hot water tank, as pre-heated water that needs much less energy before it is used or as completely heated water. For cold climate installations, the Greenward ridge vent should be filled with a water/glycol mix to prevent freezing damage.

Solar water heating generally offers one of the fastest payback periods of any green home improvement project.  This should help make it much easier to incorporate an easy, efficient system into many more homes.

link: Energy Alternatives

via: Treehugger

Knowing what we know now about climate change, it's clear that the tangled web of black asphalt roads that outlines our country is working against us.  Asphalt can absorbs tons of heat, often reaching temperatures of up to 140 degrees in the summer and the process by which it's made isn't environmentally friendly either, but there may be a way to turn that pavement into an energy resource.

Researchers at the University of Rhode Island have come up with four ways to harness the solar energy absorbed by pavement and put it to good use and they're working on ways to implement them now.

The first, and the simplest, is is to wrap flexible solar PV cells around the top of Jersey barriers that divide highways.  Those cells would power streetlights and illuminate road signs.  Cells could also be embedded in the pavement between the barriers and rumble strip.

The second is to embed water-filled pipes under the asphalt and the heat from the sun would warm the water.  That water could be piped to bridges to melt ice and reduce the need for road salt and ice-clearing trucks.  It could also be piped to nearby buildings for hot water and heating needs or converted to steam to turn a turbine.

Because asphalt retains heat really well, the pipes would stay warm even after sunset.  Tests have shown the water can even get hotter than the asphalt.

The third use is to use a thermo-electric effect to generate energy.  By linking a hot and cold spot with two types of semiconductors, a small amount of electricity can be generated in the circuit.  Those thermo-electric materials could be embedded in the road (some in sunny parts and some in shady ones) and the energy produced could be used could to defrost roads.

The fourth use is the most complex and it involves getting rid of the asphalt completely and replacing it with huge electronic blocks that contain PV cells, LED lights and sensors.  The blocks would generate electricity, illuminate lanes and emit warnings when maintenance was needed.  The researchers say this technology already exists but is very expensive.  They see this technology coming to parking lots before roadways.

via Physorg