Wind power or wind energy is the use of wind to provide the mechanical power through wind turbines to turn electric generators and traditionally to do other work, like milling or pumping. (Contributed)

Dyer: Balancing variable solar and wind energy

Kristy Dyer has a background in art and physics and consulted for Silicon Valley

Wind and solar energy have hit a critical new milestone: it’s now cheaper to build a wind or solar farm than it is to build a new natural gas plant. There is no “renewable penalty” for electricity now and responsible utilities need to start planning for a much larger share of solar and wind energy.

READ MORE: Revelstoke Dam expansion environmental review completed and waiting for ministry approval

That doesn’t mean that it is easy to build an energy portfolio heavy on renewables. Wind and solar are intermittent sources of energy: they produce electricity only as long as the sun shines and only as long as the wind blows.

READ MORE: Summerland approves solar project

It is possible to “load balance” wind and solar in the energy portfolio the same way we handle any sudden high electricity demand: using natural gas peaker plants as a backup source. These peaker plants are designed to come on during times when extra electricity is needed and then shut down quickly when the load returns to normal. Peaker plants could be run when wind energy drops or to cover for solar after the sun has gone down.

READ MORE: B.C. examines new directions for renewable electricity projects

It is also possible to improve the match between solar energy and electricity demand by merely adjusting the orientation of a solar array. Solar energy is available during the day. People use most of their power during daylight hours. This isn’t a bad match — except at six PM when everyone gets home from work. At that time the sun is low on the horizon and people are coming home and turning on appliances. This is the “duck curve” problem California faces.

Some California utility customers are on a “time of use” plan. Rather than a flat rate, they pay more for electricity at peak times and less for off-peak electricity. In these regions some contractors are increasing the size of solar arrays by 10 percent and orienting the array slightly to the west, to better match the “home from work” peak.

Wind energy benefits from “geographical diversity”

Wind energy benefits from “geographical diversity”. If you build wind farms that are separated by large distances, there is a good chance that the wind will always be blowing at some of your sites. Since wind energy comes from regions that are often far from big cities, this means you have to have large capacity transmission lines. These lines bring electricity from remote areas to the cities and allow you to take advantage of different weather at the different sites.

It would be better if you could just store the energy when you have it and then withdraw it when you need it. Battery storage has improved greatly and it has become more common to see solar and batteries packaged as “solar+storage”. The solar array to be built in Summerland is solar+storage and Summerland expects to use it to reduce peak electricity costs as well as providing power once the sun goes down.

The solar array to be built in Summerland is solar+storage

A special kind of hydro has been used since 1908 as energy storage. This “pumped hydroelectric energy storage” can be used to save money during peak periods or used to even out renewable energy. For energy savings, water is released from a high reservoir to a low reservoir during peak periods, when electricity is expensive. Then during off-peak hours it uses electricity to pump water back up to a high reservoir. Even when a hydroelectric storage plant doesn’t make money off the exchange, it is providing an essential function balancing the electric load. In combination with solar or wind, hydroelectric storage can even out the intermittent energy output of these renewables. Canada has a single hydroelectric storage site: the Sir Adam Beck Pump Generating Station in Ontario. The US has 30 sites, with a capacity of 22 GW. This type of storage only works where there are hills or mountains, providing a high and low reservoir.

Hydro power is an excellent match for intermittent renewables such as solar and wind

Hydro power in general, either hydroelectric dams or pumped storage, is an excellent match for intermittent renewables such as solar and wind. When the wind blows and the sun shines, electricity can be used from solar and wind. At night and during lulls in wind, hydro can provide load balancing and reliable backup.

Missed last week’s column?

Dyer: Financing energy efficiency

Kristy Dyer has a background in art and physics and consulted for Silicon Valley clean energy firms before moving (happily!) to sunny Penticton. Comments to Kristy.Dyer+BP@gmail.com

Kristy’s articles are archived at teaspoonenergy.blogspot.com

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