System Options
Overview:
Product Description:
Prior to installing a PV system, a building owner needs to decide what percentage of their electricity demand they would like the PV system to provide. Two basic categories of PV systems are:
Stand-alone: A stand-alone PV system uses battery banks to store electricity for use at night or during cloudy periods. This option is most practical in rural areas where connecting to the power grid is prohibitively expensive. A major benefit of this system is that a house or building’s carbon emissions from electricity generating sources are entirely eliminated.
Grid-tied: This system uses PV panels to augment the electric grid’s supply of power, to varying degrees. This allows for many system options, as it is not necessary for the PV system to provide one hundred percent of the building’s power needs.
- Zero (Net) Consumer: This system uses the infrastructure of the electricity grid as a storage medium, where the PV array produces excess electricity during daylight hours, receiving a credit from the power supplier, and buys it back at night using the credit. This system eliminates a building’s net carbon emissions.
- Maximise Roof Coverage: Recent technological developments have allowed photovoltaic cells to be integrated into building materials. In order to maintain continuity, roofs are being made entirely of photovoltaic modules or roofing tiles that have PV cells built-in (e.g. GreenPlate and PV Solar). Although aesthetically pleasing, design and site evaluation is critical for this option as shadows can have a large impact on some PV types (polycrystalline in particular).
- Maximise Payback and Net Present Value: One of the most appealing features of PV systems is their practicality for small-scale applications. However, in order to minimise the time it takes for the system to pay for itself (payback period), it is important to properly match system components and size them appropriately. e.g. : With some systems, jumping from 24 to 28 or 48 to 52 cells requires an additional inverter. This small gain in electricity production does little to offset the cost of another inverter, which is usually one of the most expensive parts of a PV system.
- Meeting a Percentage of the Demand: This is the most common application of grid-connected PV systems. The arrays may be sized to provide electricity for a certain appliance or to fit conveniently and discretely on a roof. A useful technique to consider in modifying consumption to offset the tendency to not draw limits around power consumption is to use inverters with sophisticated inbuilt communication software. Many systems have this as a standard offer and can be read via LED/liquid crystal displays on the unit or remote display panel, or on a resident’s PC where daily power generation is displayed against use.
Benefits and limitations of each system should be carefully considered when choosing a system, as several options may not be economical or spatially practical depending on the project location.
Next Step: Electric Demand
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