Renewable Facts

Solar Facts

• Each day more solar energy falls on Earth than the total amount of energy our world's 5.9 billion population would consume in 27 years (based on 1995 levels).

• Photovoltaic modules recover their environmental and recycling costs within eighteen months of their use.

• Over its lifetime, a 50 watt solar module operating in Canada will produce more than 5 MWh of power.

• The main component of photovoltaic modules is silicon, the prevalent component of sand. The amorphous silicon cells manufactured from one ton of sand could produce as much electricity as burning 500,000 tons of coal.

• Photovoltaic modules covering less than 0.3% of the land in the United States, equivalent to 25% of the area currently occupied by railroads, could provide all of the electrical power required by the United States.

•· A 1kWp PV system will prevent 136 kgs of CO2 from entering the atmosphere each month.

• Most homes in Canada use 20 – 30 kWh per day, energy-efficient homes often require only 8 – 12 KWh daily. A highly energy-efficient home could be powered by a two or three kWp solar system, while remote cottage systems typically range between 100 watts to 1.0 kWp.

• As of the end of 2010, the total worldwide installed PV capacity was 10 (GWp), a compounded annual increase of 36% since 2000. Roughly 90% of this generating capacity consists of grid-tied electrical systems.

• Cumulative solar energy production accounts for less than 0.01% of total Global Primary Energy demand while photovoltaics alone provides just 0.04% of the world's energy usage.

Wind Facts

• Global wind energy potential is roughly five times the world's current use of electricity.

• The use of 100 kWh of wind power is equivalent to the environment benefit of planting 1/2 acre of trees and not driving 3860 km each month.

•In June 2011, worldwide wind capacity reached 215 GW (WWEA publishes Half-year Report 2011). The worldwide wind capacity reached 215'000 MW by the end of June 2011, out of which 18'405 MW were added in the first six months of 2011. This increase represents 15 % more than in the first half of 2010, when only 16'000 MW were added.

•The global wind capacity grew by 9,3 % within six months and by 22,9 % on an annual basis (mid-2011 compared with mid-2010). In comparison, the annual growth rate in 2010 was 23,6 %.

Cold Weather Considerations

Battery Capacity

Battery capacity (C) is calculated as a fixed current delivered over a predetermined period of time (hour rate) at a standard 25° C until a preset low voltage (1.75 - 1.85) is reached.

A 628 Ah battery at a 20 hr rate will deliver 31.4 amps per hour, however, its 72 hr capacity is 722 Ah capable of delivering 10.02 amps for 72 hours. Cold temperature will reduce the ability of the battery to deliver either of above current outputs. At -20° C battery capacity is reduced by 40% at a 5 hour discharge rate, however, it will only be reduced by 25% if discharged over 100 hours.

While cold temperature may theoretically extend the life of a battery, extreme cold will increase internal resistance and inhibit the ability of a photovoltaic array to fully charge the battery, even with temperature compensation. To avoid this scenario, higher initial charge voltages may be necessitated.

Matrix Energy offers glazed solar collectors with PV direct DC fans that are designed to increase the ambient temperatures thus battery autonomy and provide battery ventilation. Contact us to review your requirements based upon the location, battery type, capacity and charge current.

High peak current and power

At certain times of the year, most cold climates are simultaneously cold and very bright. This combination of conditions is ideal for the photovoltaic array and it will produce far more power than would be expected in a warmer climate. Furthermore, high current occurs in winter when cell temperatures are low so array voltages - and power - are higher.

The charge controller must be able to handle these peaks in voltage and current. Battery charge controller should be specified for currents about 30% higher than would be produced by the array under standard test conditions. Controllers that track the maximum power point should use an even larger safety factor.

Low temperatures and condensation affect on electronic components

Many of the electronic devices within charge controllers are sensitive to temperature. A few devices fail at low temperatures; for example, liquid-crystal displays are often unreadable and some buttons and other input devices may not function. While most devices work over a wide range of temperatures, the characteristics of diodes, transistors and capacitors can shift slightly when all these subtly altered devices are integrated into a circuit, the result may be a charge controller or inverter that works, but with specifications quite different from those at 25°.

It is not just the cold that can affect electronics : cold climates may exacerbate thermal cycling, encouraging condensation. Condensation can infiltrate certain devices, such as capacitors, causing drift in the device's specification. It can also short circuit components operating at voltages about 70 V or higher.

Points to consider during component selection

When selecting a charge controller for cold climate, several points must be considered:

• Specifications: According to the specification, does the component function over the necessary range of temperatures ? And, if it does function when cold, will its performance remain constant? Many charge controllers operate properly, hot or cold, but specifications indicate that most inverters either malfunction or operate poorly at temperatures below 0°C.

• Simplicity: As a general rule, simple circuits are more reliable at cold temperatures than complex circuits. Circuits that operate at relatively high frequencies (say, 40 kHz or higher) will have to be very carefully designed if they are to operate when cold. They will also tend to produce electromagnetic noise that may interfere with nearby telecommunications or electronic equipment.

• Devices: As mentioned above, liquid-crystal readouts and some buttons work poorly when cold. It may be necessary to avoid these. The characteristics of other devices shift with temperature. If this is a concern, circuits built with 'military specification' devices may outperform employing 'commercial' devices.

• Potting: Some electronics are completely encased in epoxy. This 'potting' protects the circuit and avoids condensation. Certain types of potting may stress the electronic components during thermal cycling, since the epoxy will have a different coefficient of thermal expansion from the components. Many types of epoxy exist; ensure that the potted circuit has been cycled over a range of cold and warm temperatures.

• Fans: Fans, which may be part of a circuit's cooling system, may fail at low temperatures. Components that are cooled by free convection and radiation are preferable.

• Plastic cases: Some plastics are fragile at low temperature.

Solar Modules

Increase tilt angle to reduce snow build-up. The higher angle during the shorter winter months will not significantly hamper summer output.

Bypass Diodes - Series connected modules will have their output drastically reduced and cause overheating of unshaded cells if one or more modules is shaded by snow or ice. To reduce this problem connect series modules horizontally rows instead of vertical columns where possible, and ensure bypass diodes are used across the modules.

Rime Ice - Unlike thin layers of snow and mild ice which allows the passage of sunlight to the modules, rime ice may render a PV module useless for months at a time. At this time only a sufficiently large battery bank or hybrid system may counter the effect of rime ice.


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