HID ballast for PV applications
HID ballast for PV applications
The UK-based company Antares has developed a highly efficient electronic ballast for small high-intensity discharge (HID) lamps intended for use in combination with photovoltaics (PVs). The ballast was developed for the UK lighthouse authority Trinity House as part of a long-term lighthouse automation project.
The new ballast works on solid-state, single-stage conversion, and the manufacturer claims very low losses, i.e. not more than 10% of the lamp power. With a 35-W metal-halide lamp, the additional losses are only about 3W, and with a 70-W lamp not more than 7W. One ends up with a total system power consumption of 38-39 W and 77-78W respectively. Although this is lower than for standard HID ballasts for alternating current (AC) applications, it is even more interesting to compare the new ballasts with other HID ballasts for PV systems.
Typically, the latter ballasts are based on two-stage conversion. First, the low-voltage, direct current (DC) from the PV array is converted into high-voltage DC and then from DC to AC to drive the lamp. Losses can be great, especially in the DC-to-AC conversion, and the total power consumption of the conversion unit and lamp driver can be as high as the lamp power itself. Thus, a 35-W metal-halide lamp could need an additional 35 W for the power supply!
However, the new ballast is probably not the answer to the needs of the typical designer of PV-lighting systems. (See article above on PV outdoor lighting.) Since the ballast is designed for extreme efficiency and must meet very tough environmental and reliability requirements, component quality has not been the least bit compromised, according to the manufacturer. This emphasis on high quality in combination with small production volumes has resulted in a very high price of ~£500 (~US$ 700). The manufacturer claims that the extreme efficiency and high price were the result of careful consideration on behalf of the specifier, Trinity House. It was possible to establish a positive tradeoff in spite of the price since money can be saved on battery storage and PV arrays.
According to the manufacturer, if slight reductions in reliability and efficiency could be accepted, the technology could be made cheaper. For instance, Antares believes they could produce a similar ballast for the automotive industry at a cost of £70-140 if sales volumes in the thousands could be achieved.
Nils Borg
Contact:
Graham Young
Antares (Europe) Ltd.
Chiltern Hill, Chalfont, St. Peter
Gerrards Cross, Bucks SL9 9UQ, UK
Tel: + 44 1753 89 08 88
Fax: + 44 1753 89 12 60
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