Saturday, July 31, 2010

The case for a standard solar day

Here is an idea that the Department of Energy (or NREL) should develop to assist mainstream consumers adopt solar. In keeping with the Energy Star program this could be called the "Solar Star" rating. Please note: I have no idea if this is being (or has already been) tried, it just seems like it would be helpful.

The US solar industry would benefit from establishing a standard solar day (or location). This would facilitate manufactures and installers to compare products under equivalent conditions while allowing consumers to easily translate the performance of these products to their local conditions.

Let's say that a standard solar day is defined as 4.8 hours peak insolation per day averaged across the year (a more detailed/realistic standard can be constructed by adding other relevant parameters like temperature, and/or breaking the day into sub-periods). Some software programs used to estimate solar system production already incorporate rich/detailed models--but I'm willing to bet that each s/w program does this differently--a standard day could make their jobs easier too.

A person in a region that only gets 4.5 hours of peak sun on average, multiplies the standard performance of a system by 0.94 to find out how the product would perform in their location. Someone that gets 5.3 hours on average would multiply the standard performance by 1.1 to learn how the product performs in their location. Etc.

I believe this will help the industry, especially as solar becomes an economically viable option in more than a handful of states across the country. Manufacturers should be happy to demonstrate/advertise how their product performs against a single standard. They already do this to a certain extent, unfortunately the standards they use (STC or NOC) is not terribly helpful or informative for customers. Installers with a national presence should be equally happy to provide an installed cost for a "standard watt" with modifiers based on size and type of installation. Local installers could use a standard watt price to quickly/easily expand regionally. In many cases a customer could use their zip code to determine/calculate their locality modifier (if the installers don't already build that into their quotation software).


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