PVBattery Sizing

There are different approaches to sizing batteries for PV applications. For stand-alone applications, some syste m developers have sized batteries to provide up to seven days of back-up. Examples include the following militar y installations:

• Navy facilities at China Lake (334 kW PV/3,500 kWh battery) and San Clemente Island (94 kW PV/2,500 kWh battery) in California

• Air Force facilities in Idaho (78 kW PV/700 kWh battery)

• Army training areas in Hawaii (5 kW PV/600 kWh battery)

• Marine tank target range in California (69 kW PV/2,000 kWh battery)

Sizing strategy for grid-connected PV installations depends on the uses of the system and the tariffs available from the local utility. For example, power quality applications require batteries sized to provide nearly instantaneous full-power discharges for only 15 minutes of back-up. A peak shaving application for a PV system may require the battery t o boost the output of the array to meet peak loads for 1-2 hours a day. If the differential between peak and off-peak electric rates is not significant, then the battery can be sized for one hour of operation and the facility owner ca n purchase power from the grid when the PV array is not available. However, if the differential between peak and off -peak rates is significant, then an economic analysis should be undertaken to determine the optimum size of the battery system. For example, the 2.4 kW PV/25.2 kWh battery Salt River Project offered 170/kWh peak, 100/kWh shoulder, and 30/kWh off-peak experimental rates to the PV/battery demonstration it sponsored with EPRI and Sandia National Laboratories. The battery was sized to match the peak electric demand of the home (5 kW) or double the PV output (2.4 kW), in 3-hour load-shifting operations [11]. A number of PV developers optimize the PV installation, but no t the battery system, opting for 7-10 hours of battery back-up power in the event of outages. In many cases, P V installations require only minimal battery back-up to add value to PV-generated electricity. If the transmission system is heavily loaded, batteries can store solar energy which would be lost during hours when transmission service i s constrained, delivering the electricity later [14].

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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