energy use, home architect, custom home architects

Reducing Energy Use

REDUCING ELECTRICITY CONSUMPTION

Before installing a renewable electricity system, your electricity usage needs to be calculated and minimised through energy efficiency or use of alternate fuels to reduce the size and cost of the system.

Investing in energy efficiency will avoid unnecessary expenditure on system capacity.
This is particularly important for systems that must be self-sufficient. They do not have access to the electricity supply grid for back-up and you may have to resort to using expensive fuels such as diesel. For grid connected systems, using less electricity reduces the amount purchased from the grid or increases the amount that can be sold back to the grid. This saves you money.

GENERAL RULES

Use energy sources other than electricity where possible, e.g. solar for hot water. If solar is not suitable consider an efficient heat pump system.
Limit the use of high power demand electrical appliances such as cookers, microwave ovens, water heaters, room heaters, clothes dryers, air conditioners, vacuum cleaners and hair dryers.
Buy energy efficient appliances, especially fridges and freezers.
Use externally heated water from solar systems for clothes and dishwashers - do not let them heat their own water.
Use passive design building principles to reduce the need for heating and cooling.
Use natural lighting and energy efficient fluorescent lighting.
Be aware that many appliances use stand-by energy when not actually being used. Televisions, videos, clocks, computers, faxes, battery chargers, power packs, etc. still use power when they are "switched off".
Solar modules can be supplied with a frame, usually constructed of anodised aluminium, or as an unframed laminate.
More solar modules are being fabricated as building materials so that they can be integrated into the building fabric. They include solar roof tiles, wall materials and semi-transparent roof material for atriums and skylights.
It is anticipated that further development of thin film technology will lead to a proliferation of cost effective, PV coated building materials that can be integrated with the building fabric to reduce costs.
All PV modules need to be cleaned periodically to maintain their efficiency.

SITING ORIENTATION

Solar modules produce most power when they are pointed directly at the sun. It is important to install them so that they receive maximum sunlight. Ideally they should be in full sun from 9am to 3pm in mid winter.

ELEVATION

REDUCING ELECTRICITY CONSUMPTION

Investing in energy efficiency will avoid unnecessary expenditure on system capacity.
This is particularly important for systems that must be self-sufficient. They do not have access to the electricity supply grid for back-up and you may have to resort to using expensive fuels such as diesel. For grid connected systems, using less electricity reduces the amount purchased from the grid or increases the amount that can be sold back to the grid. This saves you money.

GENERAL RULES

Use energy sources other than electricity where possible, e.g. solar for hot water. If solar is not suitable consider an efficient heat pump system.
Limit the use of high power demand electrical appliances such as cookers, microwave ovens, water heaters, room heaters, clothes dryers, air conditioners, vacuum cleaners and hair dryers.
Buy energy efficient appliances, especially fridges and freezers.
Use externally heated water from solar systems for clothes and dishwashers - do not let them heat their own water.
Use passive design building principles to reduce the need for heating and cooling.
Use natural lighting and energy efficient fluorescent lighting.
Be aware that many appliances use stand-by energy when not actually being used. Televisions, videos, clocks, computers, faxes, battery chargers, power packs, etc. still use power when they are "switched off".

SOLAR MODULES

Solar modules come in two distinct categories - crystalline silicon and amorphous silicon thin film. Both amorphous and crystalline technologies are commonly used in efficient grid connected and stand alone installations.
Mono and poly crystalline modules usually have 36 solar cells in a 9 x 4 matrix connected in series to provide an output voltage suitable for battery charging.
A typical module will provide a peak power output voltage of 17V and output current of 4.7A under optimum conditions, giving a rating of 80 Watts peak (Wp). Modules can be connected in series or parallel to form an array to provide higher voltage and current outputs as required.
Crystalline solar modules are covered with tempered glass on top and a tough ethylene vinyl acetate (EVA) material at the back. The glass and backing material protect the solar cells from moisture.
Crystalline modules need to be cool. Output efficiency of crystalline PV arrays decreases by 0.5 percent per degree Celcius over the standard test temperature of 25°C. Good ventilation is required at the back of modules.
Exposure to cool breezes when siting modules is an important consideration.
Amorphous silicon is one of a number of thin film technologies. This type of solar cell can be applied as a film to low cost substrates such as glass or plastic in a variety of module sizes.
Advantages of thin film cells include easier deposition and assembly, low cost of substrates or building materials, ease of production and suitability to large applications.\
Efficiency of thin film modules is lower than that of crystalline modules but all the types of modules are price competitive. Those currently on the market degrade in output by up to 10 percent when first exposed to sunlight but quickly stabilise to their rated output.
Thin film modules have various (often flexible) coating and mounting systems. Some are less susceptible to damage from hail and other impacts than those covered in glass.
Solar modules can be supplied with a frame, usually constructed of anodised aluminium, or as an unframed laminate.
More solar modules are being fabricated as building materials so that they can be integrated into the building fabric. They include solar roof tiles, wall materials and semi-transparent roof material for atriums and skylights.
It is anticipated that further development of thin film technology will lead to a proliferation of cost effective, PV coated building materials that can be integrated with the building fabric to reduce costs.
All PV modules need to be cleaned periodically to maintain their efficiency.

ELEVATION

For stand alone PV systems (SAPS), where winter operation is crucial, the angle should be the latitude plus 15 degrees.
For grid connected systems the angle should be latitude minus 10 degrees to maximise the amount of energy produced annually. Latitude adjustments for grid connected systems in most climates fit within an acceptable roof pitch range.
Output power of an array is directly proportional to power received from the sun. This will vary throughout the day. The rated maximum output of the module might only be achieved occasionally, depending on the actual site.
System designers calculate the output energy from the peak sun hours, which is a measure of the available solar energy. It is numerically equal to the daily solar radiation in kWh/m2 (Note: it is not the same as the number of hours of sunlight). Peak sun hours varies throughout the year.Peak sun hours are usually averaged and presented as a monthly figure.
Shading one of the cells in a module is similar to opening a switch in a circuit and stopping the current flowing. This results in a loss of power from many cells, not just the one that is shaded. Partial shading can cause "hot spots" that can damage the module. This occurs in mono and poly crystalline modules but not in amorphous modules. Arrays should not be located near trees that will grow and shade the modules.
Standard solar modules are supplied with junction boxes on the back to facilitate electrical interconnection. Some modules used in grid connected systems now have leads and plugs/sockets for easier installation.
Bypass diodes are supplied within junction boxes for mono and poly crystalline modules. These bypass diodes allow current to flow through them when cells are shaded, minimising the possibility of cell damage from shading.
At night solar cells act as a resistance and current will flow from the battery bank into the module. The amount of power lost due to this process is greater in poly crystalline modules than mono crystalline modules. Blocking diodes should be installed in junction boxes to prevent this.
In SAPS the PV array needs to be installed as close as possible to the batteries to minimise the power loss between the modules and the batteries. The system designer will determine the size of the cable to minimise the power loss between the modules and the batteries.
If modules are mounted some distance from batteries, they can be wired in series to allow higher voltage and lower current. An electronic component called a maximiser is used to convert output to the correct battery voltage.
For grid connected systems the angle should be latitude minus 10 degrees to maximise the amount of energy produced annually. Latitude adjustments for grid connected systems in most climates fit within an acceptable roof pitch range.
Output power of an array is directly proportional to power received from the sun. This will vary throughout the day. The rated maximum output of the module might only be achieved occasionally, depending on the actual site.
System designers calculate the output energy from the peak sun hours, which is a measure of the available solar energy. It is numerically equal to the daily solar radiation in kWh/m2 (Note: it is not the same as the number of hours of sunlight). Peak sun hours varies throughout the year.Peak sun hours are usually averaged and presented as a monthly figure.
Shading one of the cells in a module is similar to opening a switch in a circuit and stopping the current flowing. This results in a loss of power from many cells, not just the one that is shaded. Partial shading can cause "hot spots" that can damage the module. This occurs in mono and poly crystalline modules but not in amorphous modules. Arrays should not be located near trees that will grow and shade the modules.
Standard solar modules are supplied with junction boxes on the back to facilitate electrical interconnection. Some modules used in grid connected systems now have leads and plugs/sockets for easier installation.
Bypass diodes are supplied within junction boxes for mono and poly crystalline modules. These bypass diodes allow current to flow through them when cells are shaded, minimising the possibility of cell damage from shading.
At night solar cells act as a resistance and current will flow from the battery bank into the module. The amount of power lost due to this process is greater in poly crystalline modules than mono crystalline modules. Blocking diodes should be installed in junction boxes to prevent this.
In SAPS the PV array needs to be installed as close as possible to the batteries to minimise the power loss between the modules and the batteries. The system designer will determine the size of the cable to minimise the power loss between the modules and the batteries.
If modules are mounted some distance from batteries, they can be wired in series to allow higher voltage and lower current. An electronic component called a maximiser is used to convert output to the correct battery voltage.