Introduction

Although there's a lot of talk about renewable energy sources, one should be careful about the phenomenon of hype. In the late 70's, under pressure from the first big oil crunch, the Public Utilities Regulatory Policies Act (PURPA - lots of Google on it) was put in place to enhance alternative energy sources, namely in forcing the buy-back by public utility companies of any surproduction at a fair market price. This buy-back policy is STILL IN EFFECT TODAY meaning that if you make your own electricity, whatever you don't use (for ex. if you produce solar electricity during the day but you don't use it) the utility company has to buy back from you. One dramatic downside to PURPA was the abandonment of several thousands of large windmills, mostly in the Altamont Pass area, East of San Francisco, and also East of San Diego; in effect, the technology back then posed several problems and with gas prices dropping in the 80's, many companies could not afford the cost of maintaining the turbines which were left to decay, as their removal is also prohibitively expensive.

Two issues are, as of yet, largely overshadowed by the hype on renewable energy in the US, yet they are extremely developed in other countries, Germany in parituclar. The first is that of Green Roofs: these consist of float roofs that are covered with soil and grass. The other is that of water harvesting and recycling.

Overall, one should not expect to be making a significant dent in environmental impact by adopting renewable energy sources at home in an urban area. I firmly believe that for the next five to ten years at least, these technologies would be very unlikely to self-sustain if government subsidies were to disappear.

Regardless, the real issue should be for us to CONSUME LESS; there's no curbing the population growth nor denying the right of populations from developing nations to consume the same amount that we have abusively consumed (and heavily marketed to them). But maybe if we promptly demonstrated our ability to significantly reduce our consumption addiction, we may inspire them to reduce their own before "all hell breaks loose;" climate reports, such as those of the IPCC, are only the tip of the iceberg. If the worst doomsayers are right, there's a chance much of the South USA may turn to an absolute desert within a decade!

Solar Electric a.k.a. photovoltaic (PV)

Photovoltaic arrays (multiple cells) are increasingly common on the roofs of homes and commercial buildings. Current technology (2007) yeilds somewhere around 12% conversion efficiency, meaning that the technology is still far from optimal. Although an increasing number of alternatives, the most used arrays are made of glass plates with multiple layers, that are mounted on metal frames equipped with pods that are solidly anchored through the existing roof. They are heavy and cumbersome to manipulate and hence, they should be installed on new roofing as their removal (in case of the need to re-roof) would largely increase the cost of reroofing. They often require a structural reinforcement due to their weight and to the need for them to withstand strong winds; related issues include the orientation (unobstructedly face the sun to the South), and cleaning in the event that branches or leaves accumulate under them (could lead to ice damming in severe winter storms). Advantages are a relatively small conduit for the wires (unlike solar-water heating systems) and a typical lifespan on the order of 20 years virtually maintenance free. Inconveniences include a relatively high cost, which is typically amortized over 15~20 years, which is roughly the same order of durability as that of an asphalt-shingle roof in severe weather areas (depending on subsidy amounts and sell-back value); if the roof actually lasts 30 years, then the solar system may well provide a positive entry in the owner's balance sheet. Disposal or recycling of worn-out systems will likely pose problems once the volume gets high enough, as the silicon semiconductors that make up the cells are considered toxic.
General data: "PV is cost effective for residential customers located farther than a quarter of a mile from the nearest utility line" and " A residential energy system typically costs about $8-10 per Watt" (not taking into account subsidies/government incentives (both quotes from http://www1.eere.energy.gov/solar/pv_quick_facts.html which heavily promotes solar energy).
Technological advances: flexible and thin-film photovoltaics are becoming increasingly commonplace; while they are much more convenient, they are reportedly still less durable and significantly less efficient.
Suggested links: DoE/EERE.gov: http://www1.eere.energy.gov/solar/
MIT's Technology Review on upcoming technologies http://www.technologyreview.com/Energy/18718/
In the Boston area, one expert in installing such systems is Paul Lyons: http://www.ZapotecEnergy.com

 

Solar heating systems

Solar heating systems can be divided into two categories: one consists of passive solar systems which use large masses to accumulate heat and (usually) natural convection systems to distribute it; the other consists of systems with water circulation.
Passive solar heating designs use a large window facing on a South exposure and, inside the house, a large thermal mass (usually concrete, brick, or stone). When the sun radiates through the window, it heats up the thermal accumulator and the heat stays trapped inside the house. A system of vents that are opened and closed at different times of day enables making use of this accumulated energy to heat the house at night - or during cold winter days. Obviously, this is not very suitable to regions of warm and hot climates.
Solar hot water systems are more versatile in that they provide hot water, which can then be used to wash or to heat the house by being circulated through radiators. A large array is mounted on the roof, not unlike that of a photovoltaic system, and two pipes are connected to the house hot water supply. The sun heats the black surface of the array on top of which the water circulates, before being sent down into the house, where it can be stored directly in the hot water heater or another insulated reservoir. Generally speaking, the hot water cannot be kept at its high temperature very long, so that it the most common systems use it to feed into the hot water heater, thus dramatically reducing the energy (gas or electric) required to heat the water. During the winter, if there is sufficient sun energy, the water heated by the sun can be diverted into the house heating system. Advantages: the main advantage of the system is its conversion efficiency, on the order of 40%. Inconvenients because hot water tends to be corrosive, and because the system is located outside with rather large pipes coming through the roof, there are often maintenance issues; furthermore, valves must be porperly installed to avoid backflows and diverters (in the case of heating), all leading to rather costly plumbing interventions and, due to their relative complexity, further maintenance issues.
Suggested links: Dept of Energy (again - it's amazing how resourceful they are) http://www.eere.energy.gov/buildings/info/homes/solarpassive.html
of course, Wikipedia gives pretty accurate all around information on many related topics

Wind Power

sorry, the rest is still under construction. Please contact us if you wish immediate information or assistance. Have a SUNNY Day!