Distributed solar actually means distributed generation of solar power. Solar electricity produced by households using rooftop systems is referred to as ‘distributed solar’. This contrasts with centralized generation where solar electricity is produced by a large plant and then distributed to consumers through a power distribution network (grid).
Distributed solar will normally be produced by individual owners for their own use, but any excess power may be sold to the power company.
Distributed solar system setup
A typical set up will consist of the following.
Array of Solar Panels
Solar panels (mono crystalline or poly) facing the sun with a frontal area sufficient to generate the planned amount of photovoltaic power are installed on open ground, walls, or the roof. Total solar irradiation on the surface of the earth at noon on a sunny day is about 0.8 - 2kw, depending on your location. Only about 15-20% of this energy is converted by the currently available solar panels to electricity.
Further, we are talking of peak sun hours. At all other times the power available will be less. Similarly, daylight hour will vary with the season and latitude. To top it all, not all days will be sunny. When calculating the area of panels required for a certain load all these factors must be considered, and it is generally useful to produce a rule of thumb for each region relating load to area of panels.
Mounting Structure and Down Lead
A secure mounting structure has to be provided while keeping in mind aesthetics, and any local government regulations.
A number of batteries, normally lead acid, will be connected in a series or parallel arrangement, to store the energy available from the panels, and to deliver according to load requirement. Battery capacity must be calculated keeping in mind the 24 hour load pattern, as offset against the budget.
The Charge Controller
As the output of the panels varies continuously during the day, a charge controller is interfaced between the panels and the storage battery. Both simple pulse width modulation (PWM), and maximum power point transfer (MPPT) controllers are available. The latter have an advantage in maximizing power delivered to the battery under all sunlight conditions, but have a higher initial cost.
Up to this point, the power is in direct current (DC) form. As the loads connected to the mains are all of alternating current (AC) nature, this energy must be converted to AC form at the nominal mains voltage (115 v North America, 230v in Asia and most other countries).
The inverter will normally have switching arrangements to control power flow to the load. For Grid connected inverters, any access power may be sold to the grid, while in case of need, as during the night and cloudy days, power will be supplied to the load from the utility grid.
Advantages distributed solar systems
Properly planned and installed, distributed generation of solar power has many benefits to the owner and the community in general:
- It can save the owner a lot of money.
- It will reduce the load on grid generation, transmission and distribution facilities meaning a lesser infrastructure cost and hence cheaper energy.
- It is ‘clean’. It will contribute to a ‘greener and cleaner’ environment.
- When more power is contributed by distributed sources, localized faults will have a lesser impact.
Distributed solar generation is a part of the official drive towards distributed generation from all forms of renewable energy. These include wind power, tidal power, mini-hydro power, fuel cell, biogas etc. Most of these sources have all the benefits listed above.