The coming smart grid, part one: load shifting

Published Tuesday, February 5, 2013 in the New Brunswick Telegraph Journal.

Picture this: you’re the manager of a city’s public transit system.  You oversee the operation of all the buses that get people where they’re going. 

But you have a big challenge: everyone wants to get to work promptly at eight in the morning, and go home at 4:30.  Few people want to ride in the middle of the day, and nobody rides at night.  That means you need to have lots of buses and drivers on hand to meet the demand of the morning and afternoon rush hours, but many of them sit idle for the rest of the day.  That’s expensive in terms of capital cost and labour, and it creates lots of logistical headaches.

If you can grasp the challenges created by the above scenario, you feel the pain of the folks at NB Power charged with providing New Brunswickers with an uninterrupted supply of power.

Peaks and valleys
Our power consumption is a lot like our need for transit: demand peaks twice a day.  The first peak happens in the morning, caused by all those heaters, coffee makers, toasters and hot water heaters.  The second peak happens at suppertime, caused by all those microwaves, stoves and televisions.  On the other hand, the deepest valley is in the middle of the night when most things are turned off.

The peaks are substantial.  On a cold morning last month, the difference between the middle-of-the-night lull and the breakfast peak was over 650 MW.  That’s more than the output of the Point Lepreau power plant, one of the biggest ‘buses’ in NB Power’s ‘fleet’. 

Meeting such swings in demand is a huge challenge for a power company, because firing up power plants is a lot harder than putting extra buses on the road; you can’t just flip a switch.

The typical solution is to build more power plants to meet the peaks – but that’s very costly because power plants don’t come cheap, and then they may end up sitting idle much of the time.  It’s estimated that industry-wide, 20% of power generating capacity is used just 1% of the time.  Ouch.

Load shifting
Back to the transit example: if you could get people to take the bus at times other than morning and afternoon peaks, you’d need fewer buses and drivers, and you’d save a lot of money.

NB Power and other utilities are eying that very strategy: is it possible to reduce those daily peaks by moving some of that peak demand into times of day when demand is less intense, such as the middle of the night?  The strategy is called load shifting.  When successfully implemented, it can defer the need for expensive new power plants and save lots of money.

What and how
So what types of loads could be shifted out of a morning peak?

First, heat.  Most of us turn our heat on in the morning when we get up.  But what if we had heaters that operated in the middle of the night but stored their heat until morning when we wanted it?  Such devices are called thermal storage units and they have been in use for years in places like Europe and Nova Scotia.

Secondly, hot water.  When we shower, the water we use was heated earlier and is sitting at the ready in our hot water heater tank.  The heating coils in our hot water tanks tend to start up shortly after we begin our showers, but in reality they are heating water for our next shower.  So what if hot water heaters had a timer, so that they would heat water in the middle of the night?  Most users wouldn’t notice anything, but NB Power sure would.

Load shifting is a sound strategy, but making it happen requires a few key ingredients – technology, policies, education.  We’ll get into those in Part Two.