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Will You Go "Off the Grid?"

Solar Dream Home: This Chameleon House by the Missouri University of Science and Technology was part of the 2013 Solar Decathlon, showcasing stunning examples of self-sustaining houses of the present and future.

THE ADVANTAGE OF WIND POWER OVER PV? The wind often blows when it’s dark outside. But before you buy, take a look at the national wind map published by the National Renewable Energy Laboratory (NREL). You’ll see that not every area of the United States is well suited for wind-powered living. In fact, if you live in any of the Southeast states—and you don’t have a place right on the water—wind is a long shot. You will make a lot more power with a good solar PV setup.

Photovoltaics

Looking Sharp

The race is on to build better PV cells that convert sunlight to electricity. New solar films and panels are being tested that are more efficient, less expensive and lighter than ever. The current challenge is to find a more affordable alternative to the polycrystalline silicon based panels that dominate the market. But while that R&D is going on, existing solar products are becoming more practical. For example, Sanyo recently came out with double-sided solar panels that can simultaneously provide shade (in the form of an awning), and take in sunlight on both the top and bottom surfaces.
 At the same time, the range of building integrated photovoltaics (BIPV) has exploded. That’s good news for homeowners. It means you can now have a solar generating system built right into your roof that looks like asphalt shingles or architectural metal or even clay tiles. And, as we mentioned earlier, many states require utilities to buy any leftover electricity you generate. One of the key improvements in BIPV in recent years has been the way they connect to each other and your home’s power system. The early products were co-dependent. In other words, when the connection broke on a solar shingle, the whole roof stopped producing. Newer systems have built-in redundancy in their wiring, and most are more modular, making replacement of a single faulty tile or panel less of a hassle.

Solar Hot Water

Smart Storage

The availability of extremely durable hot water storage tanks—which in some cases also serve as water heaters—has made solar hot water collection even more viable. Many tanks now include a separate closed loop of a freeze-resistant liquid. That extra loop is specifically for solar hot water—so that when the sun is shining, the solar panels on the roof heat the clean water in the tank.
But when the sun is not sufficient (or you have teenagers using up the “free” hot water) an external boiler or heating system built into the tank kicks on to make up the difference.
One of the great advantages of a solar hot water system is the relatively rapid payback. In other words, if you install this year, it may pay for itself in less than three years, especially once you figure in the tax credits and rebates available.

Cogeneration

Waste Not

Cogeneration has been common at large factories for decades. It’s basically a way of squeezing more work out of fossil fuels. Also known as combined heat and power (CHP) generation systems, these mechanical wonders put the waste heat generated by a home furnace or boiler to work making electricity. By some estimates, they achieve 90% efficiency, compared with 30%–40% from your local power station. If you’re already replacing or installing a new boiler or furnace, why not take it to another level and try cogeneration?

     
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Different Approaches to  Solar at Home
Creating electricity with either photovoltaic panels or wind turbines typically begins with production of direct current (DC) electricity. That current then passes through a transformer to become the typical alternating current (AC) used in almost all homes (aside from some RVs and boats). Most modern systems do not include battery storage, simply because battery technology has not matured enough to warrant the expense and environmental impacts. That may change in the next few years, but for now, the best bet is a grid-connected system that can later be reconfigured for advanced batteries.

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 Typical Solar Hot Water System
Using the sun to heat your home’s hot water is a time-tested idea. Typically, the liquid circulating from these panels to your home’s hot water tank is not water, it’s something that won’t freeze or boil easily, such as glycol. The heat is transferred to your fresh water inside the tank—and that’s where some of the best new technology is found. The latest insulated hot water tanks don’t rust, and the best ones lose less than half a degree per hour. That heat you collect from the sun can be stored for days.
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The freewatt Plus Warm Air System captures waste energy from a furnace component and converts it into electricity, producing 1.2 kW whenever the furnace is running. It also provides backup power during an outage.

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