Solar and Wind Power

Renewable (Green) Energy

Introduction

Renewable energy is a reliable, nearly pollution free source that can be obtained with minimal impact to the environment. Diversify energy sources by changing to a portfolio that includes renewable energy sources such as photovoltaics (PV), mini-hydro, wind, biofuels, fuel cells, geothermal, and less polluting fossil fuels such as propane.

Keyword(s)
geothermal, minihydro, microhydro, photovoltaics, solar, tidal, wave, wind

Solar Power

Heat and light from the sun is one of the most reliable events in our daily lives. Civilization has relied on the “power” of the sun for millenia. One method to reduce our reliance on non-renewable energy sources is to convert sunlight into electricity with solar panels.

BIPV – Building Integrated Photovoltaics

The main requirement for solar photovoltaics is collector area and angle to the sun. Considering the amount of wall and roof area available on every building, it is no surprise that photovoltaics are being employed on building surfaces to both generate electricity and provide other services such as weather protection.

Rack-mount PV systems or mount them directly on roof and wall surfaces. Optimize the panel’s tilt to take full advantage of solar energy. Incorporate panels into building envelope or roof design.

Watch for the commercial availability in the near future of partially transparent PV panels for use as window-shading devices.

Consider the use of large PV arrays to generate electricity while shading parking lots or other outdoor areas.

On a smaller scale, PVs can be used to economically power nighttime walkway and landscape lighting. This system saves the cost of installing an underground electrical system.

Details

Solar photovoltaic panels were originally developed for spacecraft. Arrays of photovoltaic cells arranged into panels (or windows, roofing tiles, wall panels) convert solar light rays into electricity. Thin-film technology and economies of scale are reducing the relatively high cost of manufacturing solar arrays.

Typically, commercial photovoltaic panels convert 10-25% (efficiency) of the light that reaches the panel. Electricity generated by photovoltaic panels is direct current (DC)electricity although panels are available with inverters built into the system that provice alternating current (AC).

Application

Photovoltaic systems can be optimized by orienting the panels to an optimum angle perpendicular to the sun. This optimum angle can be determined by knowing your latitude.

Optimum Panel Angle Calculation:
(Note this is for northern hemisphere, reverse sign for southern hemisphere)

Summer Solstice (June 21) Angle

(Latitude – 23 degrees) = Angle from horizontal

Winter Solstice (December 21) Angle

(Latitude + 23 degrees) = Angle from horizontal

For example:
In Rockhampton, Australia the optimum December 21st panel angle would be perfectly parallel to the ground (latitude = -23 degrees + 23 degrees = 0) or 0 degrees.

Further efficiency is possible by mounting the panels on a tracking system. In this way, the panel is in the optimum perpendicular position for the majority of daylight hours. Of course, a clear view path is necessary for the optimum energy gains to be achieved.

Checklist

  • In sunny locations, employ solar photovoltaic panels to generate electricity.
    Consider using tracking devices to optimize the efficiency of the panels.
  • Consider conventional and remote electrical uses for PV power. Devices that require constant direct current or have diurnal power needs are well suited for a PV source of power.
  • Consider utility-integrated PVs where utility demand charges are very high and there is extensive sunshine during the facility’s peak electric loads.
  • Consider PV-driven battery systems where air-quality restrictions limit the use of gas generators for emergency backup.

Wind Power

Wind energy is the fastest growing sector of the global energy economy.

Introduction

Wind is a by-product of solar heating of the planet’s surface. Fortunately, windy weather is common when storms limit solar exposure, making for a perfect complimentary energy source to solar power.

Key Word(s)
wind, energy, renewable

Details

Wind energy is the fastest growing energy source on the planet. Technological advances have made wind power competitive with fossil-fuel generation – if you have the right site for your turbine farm. Wind generates about 1 percent of America’s electricity, 15 percent of Denmark’s.

In Denmark, a country that has embraced wind energy through manufacturing and installation, the growth rate of the domestic industry is so dramatic that the entire country would be employed by 2020 if the growth continued.

The unit cost of wind energy is already comparable to other energy sources even though it receives only minimal subsidization as compared with other non-renewable energy sources.

Wind currents turn turbines that generate electricity. The downside with wind energy is that it requires some space to erect a wind turbine. Fortunately, many can still take advantage of wind energy either through the use of smaller turbines (for example 400 Watt) roof mounting units or through utility companies that provide green power.


Small or Micro Hydro

Introduction

Although hydroelectricity is considered a more environmental choice than other non-renewable sources of energy, large hydroelectric dams cause significant damage to their ecosystems. However, small micro hydro turbines can be used as a “run of the river” application that significantly reduces environmental impacts.

Details

Water power has been harnessed since the earliest civilizations for agricultural processing and latterly for the production of electricity. If you live in an old mill or have an upland stream flowing through your property, you probably have a site suitable to generate all or a significant proportion of your domestic power requirements.

The main power requirements are in the winter months, so there should be little or no conflict with other river demands. Adequate provisions may have to be made for migratory fish, and if new works are to be constructed, care must be taken with regard to the effect on land drainage upstream of your intake. If there is insufficient power to provide your needs electrically, then there is the additional possibility of using water power to drive a water source heat pump which will increase the power output by three times in the form of heat.

The power available from a stream is determined by the head and flow of water on the particular site. This power is harnessed by constructing a dam or diverting the flow in such a way that all the fall occurs in one place. Where it is not practical to construct a channel, the water may be piped and the head of water is exploited as a high velocity jet driving an ‘Impulse Turbine’. The power available is a function of the fall (head) and flow so building a large waterwheel on a low fall will only increase the cost and reduce the shaft speed but not increase the power.

Water wheels are limited to sites with a head of less than 10 meters. They are aesthetically pleasing and have good performance under low water conditions. Unfortunately, due to their size, they are both costly to build and install, largely because of the gearing required to increase the shaft speed, typically from 10 to 1500 rpm. The use of low speed generators does not help since it is the low speed end of the drive which is the expensive part.

Water turbines, on the other hand, are able to make use of a very wide range of head, from less than a metre to many hundreds of metres. To cover the full range of sites, it is necessary to make use of several different types of turbine. It is not that you cannot use one type of turbine for all sites but that each design has it economic and hydraulic area.

Checklist

  • Where available, employ micro hydro turbines to generate electricity from local streams and rivers.