Renewable Energy and the Period of Lowest Electricity Demand of the Year

We are now in the time of year with the lowest electricity demand in the Pacific Northwest, driven by our meteorology (see below).

The major peak occurs in winter, when electricity is needed to heat homes and buildings.  There is a minor peak in mid-summer, driven by air conditioner use.

With mild temperatures over the region, the demand for electricity is at a minimum during early to mid-September.

Everyone wants to maximize the use of renewable energy, such as wind and solar, so how well do they match the demand noted above?

To help answer this question, below is a plot of wind power generation for the Northwest (solar is at the noise level).

A maximum in spring and a minimum in August.   This makes sense meteorologically since most of our wind turbines are east of the Cascades, mainly on the lower slopes (e.g., Ellensburg area) or downwind of the Columbia Gorge.

Why this annual variation?   

The difference in pressure across the Cascades, which drives the westerly winds, is largest in spring because the temperature difference across the Cascades is largest then, with eastern WA/Oregin heating up more rapidly than coastal areas.  Differences in temperature drive differences in pressure, which drive the winds that produce power.

So what about the situation this year?   

To find out, I downloaded the Bonaville Power Administration (BPA) numbers for total electrical demand (load, blue) and the total from wind and solar generation (red).  The graphics are below.

Renewable energy (mainly wind) generally has a huge amount of day-to-day variability, often declining to near zero and rarely getting to 50% of the load.  Sometimes, it remains nearly zero for weeks, as in last January.  

How do we make up the difference between renewables and the demand?  Mainly hydropower, which our region is blessed with.

The detailed plot for the last week illustrated the collapse of renewables (again mainly wind)---even below our very limited nuclear power (purple line).  Demand (red line) varies substantially over the day, but hydro is sufficiently flexible to provide the necessary power throughout the day.

One thing is very, very clear.  If we want to have the energy needed for growth, electric cars. and server farms, wind energy and solar are inadequate to be the solution for the Northwest.   We need nuclear power.