Monthly Archives: December 2013

Energy Storage

The success of transitioning to sustainable energy supplies in the United States relies to a large degree on our ability to store energy produced by intermittent energy sources such as solar, wind and biomass. We have plenty sunlight and wind to go around. Conversion of biomass to a liquid or gaseous fuel is a convenient method for storing energy, but photosynthesis is quite inefficient compared to other ways of capturing solar energy. Also any biomass to energy scheme will involve burning something which always has some negative health consequences.

The future could be powered by electricity from solar and wind exclusively but how will we store the electricity for use when the sun isn’t shining or the wind isn’t blowing? Batteries are an obvious way of storing energy but are impractical for storing energy on the scale of an electric utility.

grid scale batteries

grid scale batteries

Batteries for powering transportation are in use now and will expand greatly in the future.

Most electric cars today use Lithium ion batteries. They have the best energy to volume and energy to weight ratios referred to as energy density. The problem is that even the best batteries pale in comparison to the energy density of gasoline. Liquid fossil fuels like diesel and gasoline are very energy dense and can produce 50 times as much energy as a Lithium ion battery of equal weight or volume. With current technology the Nissan Leaf, an all electric vehicle, has a range of under one hundred miles. Batteries being developed now can increase the energy density by five to ten fold, giving electric cars a range of several hundred miles.

Storing energy for the electrical grid can accommodate a wider range of methods. One of the simplest ways of storing energy is to pump water up a hill.

Pumped storage

Pumped storage

All you need are two reservoirs, one higher than the other. When energy is available it is used to pump the water to the upper reservoir. When energy is needed, the water is released, causing the turbines to reverse direction and generate rather than consume energy. The only limitation is space and geographic relief.

Another utility scale energy storage method being examined is compressed air. Just as pumping water up a hill stores energy, so does compressing a gas. In the latter part of the nineteenth century, several European cities used compressed air for energy storage. Rather than convert the energy in the compressed air to electricity, it was piped and metered to do mechanical work. Everything from motors for heavy industry to sewing machines ran on the compressed air. The major limitation of compressed air storage is the necessity of a large underground reservoir to hold the compressed air. Wind turbines in the midwest will in the future store energy with compressed air.

compressed air

compressed air

Flywheels are another method to store energy. An electric motor spins up the flywheel, later when energy is needed the motion is used to power a generator. The big advantage of flywheel storage is that it can be done anywhere. No need for a big hole in the ground or pairs of reservoirs at different altitudes.

One of the best methods to pair production and storage of energy is solar thermal. Simply heat a fluid with sunlight. When electrical energy is needed use the heat to power a generator. Power towers have a collection of mirrors pointed at the top of a tower. A fluid is circulated through the heated zone, then sent to a storage site for later extraction of energy.

All these techniques involve converting one form of energy to another, but can ultimately be used to generate electricity even when the wind isn’t blowing and sun isn’t shining.

Global Warming and Geopolitics

There is no doubt that humans are transforming the atmosphere. It is impossible to explain away the fact that burning fossil fuels and deforestation result in the considerable increase of heat trapping gases in the atmosphere. The planet is getting warmer and the oceans are becoming more acidic directly as a result of human activities. Further complications are shifting rainfall patterns, and more severe storms.

A secondary consequence of global warming is political instability. Some scientists have suggested that the “Arab spring”, the uprising in North Africa and the Middle East, was driven at least partially by food instability.

Arab Spring

Arab Spring

The cost of a loaf of bread rose steeply following a severe heat wave and drought in Russia in 2011. The political instability in the region has give radical groups such as Al Qaeda a wedge to further disrupt society and gain power.

Bangladesh, with a population of over one hundred-fifty million, depends on glacial melt in the Himalayas for fresh water much of the year. As glaciers recede, the slow metered flow of melt water changes from a somewhat constant flow to major rivers to alternating flooding torrents and droughts.

bangladesh

bangladesh

Further exacerbating the situation is the fact that much of region is at or near sea level. The combination of droughts, floods, and salinity from sea level rise could cause famine, driving the predominately Muslim population into predominantly Hindu India. Ethnic conflict would be likely.

The newest country in the world, South Sudan, came about after years of civil war in Northern Africa. The region has been stressed by an extended drought. Sudan is currently constructing a pair of dams on the Nile. Nearby Ethiopia is also constructing a dam on the upper Nile,

nile

nile

which has greatly increased political tensions with Egypt downstream. Filling the lakes behind these dams could take years and severely reduce the flow in the Nile downstream. Again the strife in the region is driven in part by a long term climate change in the form of droughts.

The loss of sea ice at the North Pole could also be a political game changer. Asian countries, principally china, are actively developing fleets of cargo ships designed to sail the polar regions, and will increase if not solidify their hegemony over international trade.

The CIA and other intelligence agencies recently commissioned a study by the National Research Council. The conclusion: climate change presents even more risk in an already unstable world. Not only is the pentagon studying the mitigation of global warming, they are also studying the relationship between climate, climate change, and political strife.

Lighting Technology

The phrase “She would rather light a candle than curse the darkness” came from a Eulogy given by Adlai Stevenson for Elanor Roosevelt. This is of course a metaphor, as the bringing of light refers to bringing knowledge to an unknowing hence dark world. Aphorisms aside, let’s be literal. Let’s talk about lighting technology.

There is good evidence that one of our ancestors, Homo erectus learned to control fire close to a half a million years ago. Fire provided heat, protection from predators, and light to extend the day into night. The campfire of Homo erectus was wood and provided much more light than heat. Light was a byproduct.

Technology expanded light production with the creation of oil lamps about six thousand years ago. Made from clay, lamps were found at numerous sites, and depending on location these were fueled by animal fat, vegetable oil or even petroleum oil from natural seeps. The related technology of candles came later, possibly originating in China about three thousand years ago. The Chinese candles were made of whale fat. Other materials for candles include tallow, beeswax, and contemporaneously paraffin, a solid petroleum derivative.

Kerosene lanterns, still in use in much of the world were common by the nineteenth century. Gas lamps, using gas as opposed to liquid developed about the same time and were popular as stationery light sources, e.g, street lamps.

All these light sources share one property – combustion. Burning something, combustion, is an exothermic process. Burning gives off heat, and if you give off enough heat you get (visible) light. Thomas Edison recognized that if you get something hot enough, whether burning or not, you get light.

Incandescent 16 Lumens per watt

Incandescent 16 Lumens per watt

His invention, the incandescent light bulb (ILB) employing electricity, revolutionized lighting and has illuminated the modern world since the start of the twentieth century.

The new revolution in lighting technology is the production of light sources much more efficient than incandescent bulbs. ILBs work by the heat, then light produced by resistance to the flow of electricity through the Tungsten filament. But it is an astoundingly inefficient process when illumination is the objective. Only about five percent of the energy consumed by an ILB produces light, the remainder is given off in the form of heat.

Luminous efficacy is measured by the product of the amount of light measured in lumens, divided by the energy to power it measured in watts. The luminous efficacy of an ILB is sixteen lumens per watt.
ILBs are cheap to produce but waste energy. More efficient are compact fluorescent bulbs (CFB).

a 100 watt equivalent clf uses about 28 watts

a 100 watt equivalent clf uses about 28 watts

These have a luminous efficacies of about fifty to sixty. They are therefore cheaper to operate but have a few drawbacks; they take time to reach full illumination especially at low temperatures, they aren’t dimmable, and they contain small amounts of Mercury which complicates disposal.

The most promising entry to inexpensive lighting are Light Emitting Diode light sources. They are everywhere already in electronic technology in the form of various indicator lights. These LEDs have now been ganged in groups to produce illumination with efficiencies of over one hundred.

100 watt equivalent LED uses less than 22 watt

100 watt equivalent LED uses less than 22 watt

LEDs don’t suffer from the deficiencies of other bulbs; they are very efficient, “instant on”, dimmable, cool to the touch, non toxic, and will become even more efficient as they are developed. The future for LED lighting is bright indeed.