Tuesday, June 30, 2009

Plug In Autos (PHEV) Grid Hero or Terror?

I saw this article about the New York Independent System Operator reporting that PHEVs won't cause a strain on the grid "as long as owners plug-in overnight". Funny, I keep hearing that PHEVs will be the savior of renewable energy, allowing for storage of wind and solar from the grid and from the home, transporting power to the workplace where they can be plugged in to run the office building on wind power stored from the grid at night, etc.. Now I see a statement about a potential strain on the grid?

Here's the problem: The typical home probably will not use more than 5 kW at any time during the day. Most of the time much less, with the peak demand around dinner time when everyone comes home and turns on the TV, the electric stove for dinner, the air conditioning during summer or the lights in winter. This causes a peak on the entire system, and the grid operator has to make sure there are enough generators - and enough distribution and transmission wires - to handle the load.

Now, it takes much more energy to move a car down the road then it does to light up a house. Most 8 cylinder cars will generate around 35 kw of power! If your PHEV has a 5 - 10 kW demand, and you plug it in when you get home - BAM - you just doubled or tripled your load on the grid!

"If vehicle batteries are charged during high-demand daytime hours, particularly in the summer, it could strain the grid and cause the need for costly new power plants, the report showed."

So the plan is to encourage millions of new battery powered cars or hybrids, and also set up a system that encourages consumers to act in ways that don't melt the grid.

Random question: How many folks want a plug-in electric car or hybrid? Now, how many of those people park their car in the garage? Oops - "there are only about 54 million garages for the 247 million registered passenger vehicles in the United States today." (pg 20 of the December 2008 report by the Electricity Advisory Committee). And of those 54 million garages - how many have room for a car? Better buy stock in extension cord companies.

Now here's an interesting dilemma - do the utilities install enough wires, generators and infrastructure to handle a potential peak from many PHEVs plugged in at one time - or do they hope that the incentives, etc., prevent that from happening?

Interesting irony - one solution to this dilemma, and many other potential grid issues, is to install large energy storage systems - like the VRB-ESS - on the local distribution circuit. This would increase capacity to handle a worst case scenario, without the need for more transmission wires, and allow for generation shifting from off-peak to peak.

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