What’s A Full-time Renewable Energy Resource?

CaliforniaGeo 7-2-18

All renewable energy sources aren’t created equal, sometimes even the most popular ones.  Let’s take a look at the similarities and differences once we understand what renewable really means.

A renewable resource is something that doesn’t run out, ever.  Our sun, the center of our solar system is the main source of all our energy and continuing biochemical and resource cycles here on earth.  [Let’s forget the fact that like other stars, ours will burn out at some point, leaving our descendants cold and lifeless—but that certainty is very far away.] 

Getting our heads back into the present, let’s remember that our hydrologic cycle, our winds, and our circulation of ocean waters are all powered by the sun during it’s 12-hour passage across the surface of the earth.  And, as many of us know, the tilt of earth’s axis as we orbit our sun is responsible for our seasonal differences in climate while influencing our daily weather.

Historically, our many human cultures have used the stored photosynthetic energy in woody plants for thermal heat (and long ago for night time illumination more akin to camping out).  Wood isn’t universally available or consistently plentiful, so it helped when drilling in the earth provided petroleum and gas that could be burned.  These resources represented decayed plant materials compressed by geology over millions of years.  The process could technically be considered renewable—but not at the rate humanity has harvested it.

Presently, technology and infrastructure is widely available that can harvest nearly unlimited amounts of energy closer to the surface than deep fossil fuel deposits.  This technology is  getting cheaper each year and improves its efficiency.  The best known of these is solar collection that produces direct current electricity.  This is not the kind of “juice” that powers your household, but in the last 40 years, we’ve learned how to efficiently transform it into alternating current by use of an inverter to provide what we need (another challenge met).

There are many people that complain about solar not being able to produce power at any time the sun won’t shine.  Some of these are fossil fuel drillers, refiners, distributors and retailers.  In overly simplistic terms, we can keep using their products just as we have been and get cancers or emphysema either before or after climate change reduces either into a secondary problem, or we can follow the wise words of the cartoon alligator Pogo, who said, “Sometimes we need to do what is required.”

The problem of solar electricity storage is rapidly being solved by advanced battery storage, and at scales that qualify it as “grid storage.”  Make hay while the sun shines, and pull from a battery when it doesn’t.  Oh, and for the fossil boys—no water consumption or emissions!

Originally, wind was only used as mechanical power for grain grinding and sailing ships.  It has come a long way since, and is now capable of producing high quality alternating current for use in our AC world.  Winds can be intermittent, but they CAN occur at night, and are capable of powering battery storage—just like solar electricity does.   

The largest and most efficient wind “turbines” are placed in offshore locations.  They are monsters in size and capability.  To give you consumers of monthly utility kilowatt-hours an idea, a single nine megawatt turbine (a continuous 9,000,000 watts) set a 24 hour record of over 200,000 Kwh in 2016.  While very popular in Europe, the offshore deployment of such generators has been slow to catch on in the U.S.  Carbon is still too cheap here, and doesn’t contain the true social and environmental costs of its combustion.  If it did, both consumers and utilities would be all over these renewable electric resources. 

The last renewable in this feature doesn’t generate electricity, but it sure can avoid much more electricity consumption than the other two sources.  It’s the geothermal heat pump (GHP) and it makes a connection to the shallow earth at depths of six to 600 feet from which it can either import from or reject to its thermal needs as a climate-controlled building.

When providing climate control or hot water heating, a GHP just happens to be the most efficient means of using electricity to concentrate and transfer heat—not to create it from scratch by combustion (like fossil fuels).  We like to describe this as a connection to the earth’s thermal battery, and it’s totally renewable and available in any season at any time of day.  Notice how no other batteries are required for its function as with the previous two renewable resources, solar and wind.  The connection to the  earth is (most often) by the use of a piped, closed fluid loop called a ground heat exchanger, which travels to and from a heat pump located on the surface, inside a building.

The near-compelling phenomenon in our climate-concerning era is that this (most efficient) heating and cooling technology can be powered with what is rapidly becoming a renewable fuel—electricity.  This includes the industrial-sized turbines or solar arrays featured above, or simply solar PV on the subject building (itself).  That means that all the necessary energy to serve a building could be gained from the building site itself, both carbonless and renewable.  This double-whammy is referred to as Zero Net Energy (ZNE).  It’s all possible with conventional building techniques and equipment, as featured in the Quincy ZNE House, where I live.