PhotoelectricityЭта страница на русском | Printable version
SystemsTo use solar panels as a safe and reliable energy source, additional components are needed: cables, a support structure and depending on the type of system (grid connected, stand-alone or back-up), an electronic inverter or a charge controller + batteries. The whole system is called the solar electricity system.
There are three types of solar electricity systems that can be distinguished:
- Stand-alone solar electricity or Solar Home Systems (SHS)
- Grid-connected solar electricity systems
- Back-up systems
Stand-alone solar electricity or Solar Home Systems (SHS)
Stand-alone solar electricity systems or solar home systems (SHS) are used when no electricity grid is available. A battery is needed to ensure the availability of electricity at night or at periods with little bright sunlight. Solar Home Systems are often used to cover the electricity needs of a household. Small systems (commercially available as a SHS kit) cover the most basic needs (lighting and sometimes TV or radio), larger systems can also power a water pump, wireless phone, refrigerator, electric tools (drill, sewing machine, etc) and a VCR. The system consists of a solar panel, a control unit, battery storage, cables, the electric load and a support structure.
| 1. | solar panels | 3. | battery |
| 2. | controller | 4. | appliances |
How much PV do I need for my house?
How much PV you need depends on your power loads and their duty cycles. If you wanted to completely replace your current electrical purchases from the utility with a PV system, you could look at your kWh usage on your electric bills for a year, calculate a daily average, and divide that by the number of average daily sun hours for your location. (3600 kWh/yr divided by 365 days/yr equals approximately 10 kWh/day, divided by 5 sun-hours per day (for locations in middle America), equals 2 kW. This would indicate that a 2-kW system would, over the course of an average year, produce enough energy to replace the power you are currently using.
However, if you design an energy efficient home, you could cut the annual electricity usage dramatically, reducing the size of the system. In the real world, the majority of home systems range from 1 kW to 2 kW. Where you live, if you are on the grid or off, and how you live, will dictate the size of your system, and its ultimate cost and value.
Solarhome.ru has a simple tool that can be used for system sizing: the calculation of the number of solar panels and batteries. Although a handy person can do much of the work, all electric connections should be made by a trained professional/installer.
Grid-connected solar electricity systems
When the electricity grid is available but electricity from a clean source (solar) is desired, solar panels can be connected to the grid. Provided that sufficient panels are placed, the appliances in the house/building will then run on solar electricity. A grid-connected solar electricity system basically consists of one or more solar panels, an inverter, cables, the electric load and a support structure to mount the solar panels.
| 1. | solar panels | 3. | grid |
| 2. | inverter | 4. | appliances |
Configuration of a grid-connected solar electricity system
An inverter is used to connect the panels to the grid. Some panels (so-called AC modules) come with an inverter for grid connection built in. The solar panels can be mounted on the roof under the optimum tilt angle (see tilt angle and orientation) with a support structure or aluminium frame. Simple systems with AC modules and prefab support structures are increasingly commercially available for do-it-yourself purposes. Although a handy person can do much of the work, all electric connections must be made by a trained professional (check with your utility or supplier).
Examples of a grid-connected systems placed on a flat and tilted roof.
Building-Integrated PV (BIPV)
Integrating PV into building structures holds the promise of extensive market penetration in developed countries, replacing conventional facade and roofing materials and avoiding the cost of support structures. These systems include crystalline modules integrated into roofing systems and used as 'eyebrows' over windows, and glass-on-glass modules used in skylights and view walls; and amorphous silicon modules, both opaque and semi-transparent, used in curtin wall systems.
Utility Systems
Utilities are using PV in many applications, including large centralized generation, transmission and distribution support, demand-side management, distributed residential and commercial systems, and remote, stand-alone monitoring systems.
Demand-side management (DSM) systems have particular value because they produce power for the grid at the times of the utility's peak demand (when power is the most expensive.
Transmission and distribution support has value because utilities can install PV near substations or at the end of overloaded lines, eliminating or delaying the need for costly upgrades.
Back-up systems
Solar electricity back-up systems are used when electricity from the grid is available but unreliable. The solar electric back-up system can be used to provide electric power during periods when there is no electricity from the grid (blackouts). A small solar electric back up system can provide electric power to cover the most important needs such as lighting, computer and telecommunication (phone, radio, fax, etc) equipment. A larger system can be sized to power the fridge during a black out. The more power the appliances take and the longer the black outs normally last, the larger the solar electric system needs to be. Although a handy person can do much of the work, all electric connections must be made by a trained professional (check with your utility or supplier).
| 1. | solar panels | 4. | grid |
| 2. | inverter | 5. | appliances |
| 3. | battery |
The system consists of a solar panel, a control unit, a battery storage, cables, an inverter, the electric load and a support structure.
Other applications
Hybrid Power Systems
Hybrid systems typically include some combination of PV, wind, and diesel generators, along with controlling electronics and battery storage. The reasons for these systems include making maximum use of the available resources (wind and sun), serving critical loads (telemetry and communications), and supplementing existing equipment (reducing the duty cycle of an existing diesel generator).
Consumer Product Power
Most solar-powered consumer products (calculators, etc.) use very small amorphous silicon PV devices to provide the power necessary for their operations.
Space Power Systems
Photovoltaic systems have been used to power satellites and space probes since the Vanguard I launch in 1958. The critical issues in space power systems are weight and reliability: weight, because of the high cost of boosting equipment into space; and reliability, because servicing a system is difficult (impossible, until recently) and expensive. Because these issues are more important than cost, the technologies are typically more exotic than those used in terrestrial systems.
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