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SolarEdge Makes Impossible Installations Possible

Mr. Eitan Reem who lives in the peaceful Kfar Vradim village in northern Israel, wanted to join the constantly increasing community of home owners and farmers who install solar photovoltaic (PV) systems on their roofs. He approached Solgal Energy, one of the leading PV installers in Israel who reviewed the house’s position and design and recommended the installation of a 4kW system on the southern façade of the roof. The Israeli FiT allows installation of systems up to 15kW on residential roofs, which prompted Dov Kotlar, Solgal’s CEO, to examine the possibility of utilizing the entire roof area to install a maximum capacity system. “We relied on two guidelines”, says Kotlar, “the first – the larger the system, the lower the cost per kWp. Therefore, despite the decrease in efficiency in non-south-facing facets, an optimum can be reached in which the ratio between system cost and system throughput remains attractive. The second – we are going to install the innovative SolarEdge system, which enables production of up to 25% more energy and full roof utilization, in every direction. The SolarEdge system removes the known system limitations and enables installation of strings of different lengths, on different facets and in different orientations and tilts as well as installation of different solar module models, both under optimal conditions and under partial shading conditions.”

The SolarEdge distributed power harvesting PV system includes power optimizers that are integrated into each and every solar module, and enable performance of each module at its own optimum at all times. Power optimizers perform constant tracking of their respective module’s Maximum Power Point (MPP), so no module is dependent upon performance of neighboring modules. Unlike PV systems with a centralized inverter, in a SolarEdge system modules with low performance do not drag down the performance of other modules in the same string, and in fact have no effect on the performance of other modules. In addition, power optimizers maintain fixed string voltage, so that the inverter’s input voltage is always constant and equals the optimum inversion voltage. For this reason, the system can have strings that differ in length and other properties. The power optimizers also collect module performance measurements and allows remote monitoring of the PV site, through a virtual site map in the monitoring portal. Unlike any other distributed PV system, the SolarEdge system includes a highly efficient solar inverter as well. The inverter was specifically designed to work with power optimizers and was recently acknowledged by the California Energy Commission as the most efficient single phase inverter in North America.

15 kWp SolarEdge system installed on four facets of  the roof by Solgal Energy / Photo: Alon Levite

Based on the above-mentioned assumptions, Solgal examined the possibility of installing solar modules on all 4 facets of Reem’s roof. Using several simulators, it was discovered that installation of an additional 4kWp on the eastern facet, which has a slight southern orientation, will produce energy with only 8% less efficiency than a completely south-facing facet. Installation on the western facet, which has a slight northern orientation, will cause energy loss of 22% compared to a south-facing facet, and installation on the northern facet will cause a 32% power loss compared to a south-facing facet. Kotlar explains “After analyzing the cost effectiveness of the system it was found that the entire system will produce energy at 85% efficiency relative to a system of the same size installed on a southern facet. Most traditional centralized inverters do not allow the connection of modules on different roof facets to a single inverter, but with the SolarEdge architecture we were able to utilize all four facets of the roof, so that the price per installed kW is beneficial, in spite of the decreased production”.

“Full roof utilization and excellent system performance”. Dov Kotlar, CEO of Solgal Energy, in front of the Reem house / Photo: Alon Levite

Due to the unique geometric shape of the Reem roof, using solar modules of a single make and model would allow only partial utilization of its area and installation of a 12kWp system only. To fully utilize the roof and install a complete 15kWp system, the maximum permitted by the Israeli FiT, smaller modules were needed, which would have been impossible using a single traditional centralized inverter. Because the SolarEdge system allows tracking the MPP per individual module, it enabled installation of 3 different module types, making the total roof area available for installation and enabling 25% additional peak power.

On July 5^th 2010, the Reem PV system was connected to the grid. The 15kWp system includes 25 Suntech 280W modules, 34 Suntech 210W modules and 4 Suntech 185W modules. A power optimizer is installed on each solar module, and the whole system is connected to 3 single phase SE5000 SolarEdge solar inverters. The system is designed as follows: 4kWp are installed on each of the south, east and north facing facets. An additional 3kWp are installed on the western facet. Initial readings show an average production of 6kWh per kWp per day. “The system’s yields are fantastic even when compared to ideal systems installed only on southern facets” says Dov Kotlar. Eitan Reem, the system owner, adds: “without Solgal Energy’s creativity and courage we would not imagine that such a large installation is possible on our uniquely shaped roof. The combination of Solgal’s proficiency and SolarEdge’s innovative solution allows us to reduce the time to return on our investment and to enjoy green, clean energy from day one”.

100kWp SolarEdge system installed by GreenTops  on Bet-Yamin’s roof

The SolarEdge system enabled another, previously impossible, installation. The owners of the Bet-Yamin commercial center in the city of Ashkelon, Israel, wanted to install a PV system on the building’s 1,700 sqm. roof. Over the past two years many installers examined the roof which is heavily shaded by rails, elevator shafts and staircases, and all came back with the same answer – impossible, too much shade to make the investment worthwhile, the full roof area cannot be utilized. The building’s owners did not give up, and asked for one more opinion from Moti Avni, CEO of GreenTops, one of Israel’s largest installers, with 7MW of installations in Israel. GreenTops, which distributes the SolarEdge systems in Israel, recommended installation of a 100kWp SolarEdge system on Bet-Yamin’s roof. “The SolarEdge system is the only system that enables installation of solar modules on the roof of Bet-Yamin” says Moti Avni. “Installation of any other inverter would have produced as little as 50% of the current energy throughput, which would make the entire installation uneconomical”. 4 months and 70,000kWh after, the Bet-Yamin system was connected to the grid, the economic viability of the SolarEdge installation exceeded expectations.