Machine Design

Leland Teschler's Editorial: A View of the Future From a Housetop

A factory tour at Energy Conversion Devices Inc. could well make you think you are seeing the future.

That certainly was my reaction as I stood in one of the company’s facilities holding a shingle with thin-film solar cells built in. The machine behind me was cranking out solar shingles by the hundreds. Eventually many of us could have these things wired into our roofs. The idea would be an expensive proposition today, but the costs are going in the right direction.

There will be a problem, though, when everybody on the block is plugged into an alternative energy source. On a sunny day at noon when most people aren’t home, those solar cells will generate more electricity than most homes need. They’ll all want to send power back to the substation serving them. That would be impossible today. Substations just aren’t designed to work with a net power flow that is “backwards.”

There are ways to make “backwards” flow feasible, but they aren’t free. “Usually a distribution system can handle about 15% of its rated capacity in distributed generation without having to make any changes,” says Energy Power Research Institute Senior Technical Fellow Roger Dugan. “A technical solution can address the situation of larger capacity. But the bigger problem is in figuring out who will pay for those changes.”

The who-pays problem is handled today by giving the last alternative energy owner on the system a bill. If your solar cells are the ones that send the substation over the magic 15% level, you could be in for an electrical shock of a different kind. The utility may dun you to cover new line reclosers, step voltage regulators, and engineering work which is “not trivial,” says Dugan.

There are more equitable ways of handling the costs, but the most obvious approach is politically incorrect: Penalize distributed generation households by paying them a below-market rate for the electricity they generate. The difference goes into a kitty for handling changes in distribution made necessary by solar and wind power.

It’s unlikely that many alternative energy fans will confront this scenario anytime soon, though, simply because the costs of alternative energy remain steep. “Solar photovoltaic systems on roofs are usually only 6-kW peak output at most,” says Dugan. “The cost of system would run about $15,000. That’s about all most people can afford today.” Still, he admits, “If there were a technology breakthrough that would bring the price of those solar shingles down to where they would be no brainers, then we might have to rethink some things on the distribution side.”

Speaking as a guy who just found out he needs a new roof, I’m not eager to see this day come, even if I get a break on my utility bill. If you think a reroofing job is expensive now, wait till you see what it costs when there are solar cells in the shingles.

— Leland Teschler, Editor

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