Medicine For People!

January 2017: Adding Up Renewables

Adding Up Renewables

According the American Wind Energy Association, this year the United States is #1 in the world for wind energy production. We produced almost 5% of our electricity from wind power, enough to power over 17 million typical homes.

The Solar Energy Industries Association reports that most of the increase in electrical power came from solar for which the price falls each year. We have nearly 32 gigawatts of solar capacity now installed in the United States.

All this is very good news, but does this mean that renewable sources can solve our energy problems in time?

Sustainable energy without the Hot Air

Available in print, you can also download it for free (370 pages in full color!) from


This book by David MacKay, Britain's most respected authority in the field of energy production and climate, can help you decide. You say you have no time for another book? Then watch his vivid 20-minute TED summary.

During his talk, he tells how he was once accused of being "anti--renewable energy." He responded that he is definitely in favor of renewable energy sources; they are the keystone of any real sustainable energy program. But he is also pro-arithmetic.

Let's look at some arithmetic while learning more about how our electrical grid works.


Supply and Demand

Energy Team


Not every country can rely on power that comes out of the wall socket 24/7/365. That we can depends on dispatchers such as those pictured above at the PJM Interconnection, which coordinates the movement of wholesale electricity in the mid-Atlantic region.

Hourly Electricity Demand in the PJM Interconnection


This graph shows electricity demand over one week. You are looking at 18 billion dollars worth of electricity and big changes in demand—a doubling of need between early morning and evening.[1]

PJM's power comes from these sources:

Historical Power Generation during 2010


Coordinating all these sources takes a lot of work, hence the high-tech control room pictured above. Few of these sources can be turned on in an instant. But when millions of people get home from work in the same 15-minute period and turn on a few million air conditioners and television sets, a lot has to happen in a hurry. PJM controllers dispatch electricity from these sources:

Nuclear (blue): These cost little extra to run at full power and are on almost all the time.

Steam (brown): Coal is relatively cheap, so it takes up most of the slack.

Combined cycle (green): Burning natural gas more efficiently than the older type of gas turbine generator, these ramp up fairly quickly to meet high day-time demand.

Hydro (purple, barely visible): Hydroelectric power is not much available in the PJM region, but turns on quickly when demand requires.

Pumped hydro (blue): During the night, or when demand unexpectedly falls below supply, excess electrical power pumps water up to reservoirs. During the day, this water runs downhill again to generate about 80% of the energy invested. Currently the US can store about 2% of what we generate.

Gas turbines (orange): Gas turbines cost the most, but can ramp up and down rapidly. They help fill the gaps at peak demand.

The whole system has the complexity of a chess game. There are many factors to consider. Consumers can turn a million electric heaters off and on within minutes. They don't worry about the load on the electric grid.  PJM does the back-stage work to allow us to do this. Turning a coal plant on or off puts significant wear on the equipment and requires time and money). Pumped hydroelectric ramps up quickly but costs more. Gas turbines can ramp up fast if needed, but will exceed emissions standards when they do.

Here in our Pacific northwest, hydroelectric power levels must balance the needs of the grid against the needs of the rivers, including salmon, commercial navigation, riverside industry, irrigation, and so forth. Grid operators balance many other variables including temperature forecasts, power plant maintenance schedules, industrial demand, and power costs.

Wind and solar currently pose a challenge in that we humans aren't able to turn them on and off. The difficulties are demonstrated in the "California Duck Curve."

California Duck Curve


As noted, power demands fall at night and rise during the day. We deal with that that by combining cheap baseline coal and nuclear with more expensive but more flexible gas and hydroelectric power. California, in the front rank of solar generation, is finding the daytime hump turns upside down. One peak has become two: the early morning demand as people get up in the dark to go to work, and another when they get home.

California electricity providers struggle with this. They greet the dawn providing 18,000 MW (megawatts), aka 18 gigawatts, of baseline power from their economical coal and nuclear sources. More solar coming online in the middle of the day means difficult and expensive down-powering of these baseline plants. Even worse, people come home as the sun sinks and solar output plummets, so the utilities have to ramp up power faster than their generating equipment can easily accomplish.

Furthermore, during the day they may need to cope with fluctuations in solar output, as shown in this graph from Hawaii. This is a large plant with some ability to store electricity and smooth out variations, but the power output still wanders around dramatically.

How cost of solar energy is calculated


Proposed remedies include charging you more for power when grid needs ramp most quickly, increasing energy efficiency in individual homes, substituting solar thermal for photovoltaic solar, energy-storing water heaters and air conditioners, and more. Each of these requires significant work. Homeowners orient solar panels towards the south to maximize their own return on investment, inadvertently worsening the duck curve as more panels come on line. As utility rate-payers, however, we increasingly need those panels to be oriented more westward to lessen that costly late-day ramp.

Points to consider:

  • Providing constant power to consumers requires balancing of many power sources, some inflexible and cheap, some flexible and costly.
  • Traditional sources are controllable; renewable sources (wind, solar, tidal, etc.) less so.
  • Electricity demand over time does not always match supply from renewable sources.
  • Adding renewable sources into our current grid poses challenges that will take years to overcome. For example, storing electricity is expensive.
  • Actual electricity available at your wall outlet is not the same as advertised capacity. Yes, the USA got 32 gigawatts of new capacity from solar in 2016, but given nights, clouds and winter days, the actual output is about 20% of that, as this graph shows.


A Rational Plan with Maximum Renewables

Sustainable Energy - without the hot air

Remember this?

Your free book with a wealth of numbers and calculations? This guy used all that research and calculation to figure out how to squeeze as much renewable sources into his country of Great Britain as possible. He considered cost, contemporary feasibility of the technology, space constraints, a modified NIMBY factor, industrial capabilities, the various political interests, and carbon tax proponents.
As no similar analysis for the USA has come across my radar screen, let me just show you this one.

Renewable Energy Plan


The caption rewards a careful reading. Notice the eight yellow hexagons in the lower right of the map. This is the actual area of solar power plants that need to be constructed in the deserts of Northern Africa, the power brought up to Great Britain in high-voltage direct current (HVDC) power lines constructed through Spain and France. This plan also requires a six-fold increase in nuclear power. The plan includes measures to store energy from wind and solar.

We have more real estate here in the USA and more sunshine, and yet we face the same calculus. Our major solar facilities, for instance, will have to go somewhere in our southwest, somewhere between the national parks, private holdings, Native American reservations, and public lands.

Yes, we will find a place. Yes, we'll figure out ways to tame the Duck Curve, the storage problem, the NIMBY problem, and all the other problems. Sadly, it won't come as easily as turning a faucet handle labelled "solar and wind."

Wind and Solar

The 5% of our electricity from wind power mentioned at the beginning of this newsletter? That translates to 190 terawatt hours, an amazing and reassuring quantity. But it is still only in the range of 1% of total US annual energy use (about 28,000 terawatt hours), because only about 40% of our energy use comes as electricity as illustrated below.

US Energy 2009


You are Not Alone

Evaluating the press releases on energy advances can be eye-glazing. You can blame it on

  • Unusual prefixes such as giga- tera- and mega-
  • Shifting units such as British Thermal Units, watts, watt-hours, kilowatt-hours and be grateful when the geeks don't start mentioning joules.
  • Renewables often expressed as percent's of US electricity supply, when 60% of our energy doesn't involve electricity.
  • Expressions such as powering so many homes, which amplifies the implied effect of a given power source.
  • Up-to-date numbers are rarely easily available. The graphic above, for example, telegrams vital information but current numbers are surely slightly different.

The graph also tells us that while 17 million typical U.S. homes are now powered by wind, we need to remember that residential energy makes up only 10% of the U.S. total requirement.

Charge to the Graduating Class

The message is this: Changing our energy supply from civilization-threatening to sustainable requires more time than usually realized, time during which our environment carbon builds to ever more unsafe levels.

If you have followed along with this series, though, you should have the background information than leads me to join my voice to those urging us to employ nuclear power as part of our transition to a carbon-free future.

Next month we'll continue this series with a review of nuclear waste, economics, and safety.


[1] That is at typical US prices of 12 cents per kwh. European prices are up to three times higher, Danes and Germans paying about 30 cents per kwh, and others less as you can see below.





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Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.