A recent survey in the UK determined that an overwhelming majority of people want their homes to be environmentally-friendly and want to save money on energy bills. Yet, 58% feel that photovoltaic panels protruding from a roof are unattractive, and 65% would avoid adding solar panels for that reason. While psychologists wrestle with the cognitive dissonance in those beliefs, Solarcentury decided to create better looking solar panels. Its product line includes PV panels that double as roof slates and tiles, and the company’s latest product, the Sunstation, is a fully-integrated PV system that doesn’t sit above the roof shingles - its panels are installed flush with the roof.
Sunstation
All panels meet the requirements of standard roof shingles while still generating electricity. According to John Sturgeon, head of product development at Solarcentury, the weather-tight products demonstrate resistance against fire, wind, snow loading, and hail. Sunstation has been tested with a hailstone of 25 mm (~1”) at 23 m/s (51 mph), without showing any defects.
Solar shingles have been around for a few years, so there’s not much new in that regard. For a new construction or a replacement roof, solar shingles provide a cost-effective way of integrating PV into the building. But the Sunstation caught my eye because it’s a retrofit option; it’s still a traditional set of PV panels, but the panels can replace a small set of shingles instead of the entire roof.
Sunstation panels are made of monocrystalline silicon - slightly more expensive than polycrystalline but also more efficient. That extra efficiency helps to offset the slight loss of power caused by the lack of an air gap between the panel and the roof. Traditionally, PV panels are mounted to rails that sit an inch or two above the roof. This allows airflow to cool the panels on both sides, which improves their output. Sunstation panels mounted directly to the roof generate about 3% less electricity than the same panels mounted with an air gap; that’s the trade-off between aesthetics and efficiency.
Sunstation is sold as a complete package, including the inverter, balance of system hardware, and professional installation. Its cost ranges from $2.45/watt to $3.28/watt depending on the size. A low-end 2 kW system runs about £4,200 (~$6550); that should supply more than half of the electricity used by a typical UK home. At the high end, a 4 kW Sunstation costs £6,300 (~$9800). The systems are designed to be grid-interactive, taking advantage of net-metering to help defray the cost. They can also be integrated with behind-the-meter storage and, depending on the inverter, are capable of disconnecting from the grid (in the event of a power failure) and running in stand-alone mode.
The Sunstation web site includes a calculator that allows potential customers to estimate their return on investment. The estimator takes climate, projected inflation, net-metering, and electricity rates into account, and assumes a 0.7% annual degradation rate on the PV panels. It also accounts for potential non-warranty maintenance, including inverter replacement after about 10 years. The estimation tool is similar to the EnergySage site in the US - a user enters her address and answers a few simple questions, and the software sizes up a system and does a financial analysis.
Like other building-integrated photovoltaics, Solarcentury’s products trade efficiency for appearance, which hopefully results in more people using PV. When I compare Sunstation’s 16% efficiency with the 0% efficiency of non-PV shingles, Sunstation becomes that much more attractive.