Recyling waste heat to power

smokestack, waste heat

A fossil fuel electric plant in Arizona

You’ve heard the advice not to run your oven or dryer on a hot day.

Why? Because much of the heat they generate gets out into the room. It’s wasted.

You can’t keep your laptop on your lap very long. It gets too hot. More waste heat

Imagine the heat wasted in industrial processes!

For just one example, when you see a smokestack, the smoke has passed through technology that burns nasty stuff like dioxins and volatile organic compounds. Which makes it even hotter than it was before. And it’s not only smokestacks that release waste heat into the atmosphere.

But what if we could capture that heat and put it to work? Turn waste heat to electric power?

We can.

We’ve used one technology to turn waste heat from large-scale industrial processes to electricity since the 1970s by using it to run a turbine. In other words, it uses waste heat instead of combustion or nuclear reactions, but otherwise operates turbines the same as traditional power plants. Traditional power plants can use their waste heat by installing an additional turbine before the steam reaches the condenser.

Converting waste heat to electricity uses no additional fuel. It releases nothing into the atmosphere that wouldn’t have been released anyway. It makes sense both economically and environmentally.

A newer technology, thermoelectrics, does not need a turbine. It converts waste heat to electricity directly.

Do you camp, grill in your back yard, or have a fireplace? You can buy and use one thermoelecrtric product right now. More consumer applications will probably follow quickly. Thermoelectrics makes possible a whole new kind of recycling.

Waste heat to power using a turbine or engine

waste heat to power diagramSteam turbines have worked effectively for more than a century.

There are multiple designs, but basically water boils, steam turns a rotor, and with or without a condenser the steam becomes liquid water and returns to the boiler.

Scotland-based Heliex Power distributes waste-to-power steam turbines in the UK and five other European countries. Heliex installations are well enough insulated that they can be installed indoors.

Steam turbines require high heat. Less than 10% of the heat generated by industry is hot enough to operate a steam turbine.

A newer technology, the organic Rankine cycle (ORC), vaporizes and condenses refrigerants, which boil at a much lower temperature than water. Some of them can work at temperatures as low as 200º Fahrenheit.

General Electric and Electratherm have installed ORC turbines in at least ten different countries. Ener-G-Rotors use ORC differently. Instead of operating a turbine, the refrigerant turns a simple rotor mounted on bearings, which make it nearly frictionless. MIT and the EPA have both described this new technology.

Echogen licensed a CO2 heat pump from NASA and after its first prototype figured out how to use supercritical CO2 to operate a generator instead of a heat pump. CO2 boils and vaporizes at a much lower temperature than even refrigerants.

Supercritical CO2 achieves a temperature where the CO2 isn’t quite a gas, but isn’t quite a liquid, either. The company introduced its first commercial produce in December 2014.

stirling engine waste heat to power

Beta type Stirling engine. There is only one cylinder, hot at one end and cold at the other. A loose-fitting displacer shunts the air between the hot and cold ends of the cylinder. A power piston at the end of the cylinder drives the flywheel.

Cool Energy [LINK], on the other hand, is resurrecting an old technology, the Stirling engine, that was invented in 1816 and ultimately proved unsuccessful.

It’s an external combustion engine that’s much more economical than steam engines. It’s a piston engine that operates on compressed air at a lower temperature than steam. It can use almost any heat source.

When Stirling engines failed (which all of the industrial scale engines did), the result was much less catastrophic than the explosion of a steam engine.

They worked well on a smaller scale, such as pumping water, until electric motors became available.

The technological and material roadblocks to the Stirling motor’s success were all solved by the end of the Second World War. Various companies tried without success to find a commercially viable use for them.

Cool Energy’s waste heat to power application is expected to become available commercially later this year. It will be interesting to see if the Stirling engine will finally be competitive with other technologies.

Thermoelectric generation

thermoelectric module waste heat to power

Thermoelectric module

The junction of two dissimilar materials produces voltage if they are different temperatures.

To be a practical power source, thermoelectric materials must conduct electricity well, but conduct heat poorly.

That combination keeps the hot side hot and the cold side cold.

NASA developed a thermoelectric generator for the Voyagers 1 and 2, which launched in 1977. Thirty six years later, Voyager 1 left the solar system, with its thermoelectric generator still working.

Decay of radioactive material provides heat, and semiconductors made of rare and expensive materials turn it into electricity.

Nanotechnology and a much more common and inexpensive semiconductor, tetrahedrite, have made wider application of thermoelectrics practical. Scientists at Michigan State University developed the technology and licensed it to Alphabet Energy.

A circuit of thermoelectric materials that produce usable electricity is called a thermoelectric module. A thermoelectric module requires both a positively charged and a negatively charged semiconductor, configured to be in series electrically and in parallel thermally.

In order to be useful to turn waste heat to power, it must be able to withstand the stress of multiple thermal circuits in very large temperature gradients over time. Thermoelectric modules that are both engineered properly and made with economically feasible materials form the basis of a thermoelectric power generator.

A thermoelectric power generator requires a dependable heat source on the hot side and a suitable means of cooling the cold side. Various machines used both in industry and in personal activities provide an infinite variety of heat sources. Car exhaust can serve quite nicely. Air, water, or a refrigerant can provide the cooling.

The generator, like a solar array, produces direct current. Where alternating current is needed, the generator’s output goes through an inverter.

Alphabet Energy has designed and built the world’s largest thermoelectric power generator for use in the oil and gas industry, mining, defense, transportation, and manufacturing. It’s the size of a shipping container, but its construction comprises multiple thermoelectric modules. A single module would be useful for much smaller applications.

If Alphabet Energy claims the largest thermoelectric generator, LairdTech claims the smallest. It has developed a thin nanoscale thermoelectric film to create a device that puts out electricity measured in microwatts.

Such a small generator could capture heat within thermal environments that produce, and therefore waste, heat at much lower temperatures than industrial applications. The device is designed to provide power to distributed devices, such as remote sensors.

At least one consumer thermoelectric product, the PowerPot, is available already. More will surely follow. The PowerPot’s heat source can be a campfire, an outdoor grill, a fireplace. It looks like an ordinary cooking pot with a thermoelectric plate on the bottom. Filling the pot with water provides the coolant.

Even if the water boils, it still has a much lower temperature than the heat source. Melting snow, being much colder, allows the device to produce much more electricity.

The PowerPot produces enough electricity to charge a cell phone or any other device charged with a USB port. It begins to charge within seconds of being placed on the heat source. Its built-in regulator means that the variability of the temperature of the water doesn’t matter.

The electrical output is always the same: 5 volts and up to 1000 milliamps, the most any USB charged device can handle. The devices charge in the same amount of time with the PowerPot as they do plugged into a wall socket. It is therefore a very useful product on camping trips or in event of a power failure.

Choose which PowerPot is best for you.

Photo license statements:
Electric plant. Source unknown.
Waste heat to power diagram. US Air Force.
Stirling engine. Public domain from Wikimedia Commons.
Thermoelectric module. Pubic domain from Wikimedia Commons.

What’s Real in Corporate Sustainability?

green barcode, corporate sustainability

Bar code made from grass blades isolated on white

You’ve seen the product labels. You’ve seen the claims on commercials. Corporations say they care about the environment.

Putting eco-friendly statements labels and commercials and then not doing anything about them is known as greenwashing.

How is a consumer supposed to know a company’s real commitment to sustainability?

You have to dig a little bit, but the news in encouraging. Corporate sustainability and social responsibility are good for the bottom line. Corporations now have more ambitious goals than they used to, so ambitious that they must call for outside help. Continue reading

11 Simple Hacks to Create a Greener Workplace

green-workspaceContributed by Alexandrea Roman

Are you doing what you can to go green at  home? What about your workplace?

Going green at the workplace is good not only for the environment, but also for businesses and their employees.

For businesses, a major benefit is the overall reduction in costs. Sustainable practices often result in lower energy consumption, which in turn cut utility bills. Continue reading

Our Costly Neglect of Drinking Fountains

drinking water fountain

Drinking fountain in a botanical garden

Have you thought much about drinking fountains, or even seen one lately?

They used to be everywhere—in all kinds of public buildings and in parks. Building codes specified how many drinking fountains a public building should have.

They still do, but this year the International Plumbing Code cut its number in half. Building codes in most American cities follow the IPC’s recommendations.

We don’t see as many drinking fountains in recent decades. People buy bottled water instead. That’s bad for the environment and not especially good for public health.  Continue reading

Making DIY home cleaners

DIY home cleaners, ingredients

Some common ingredients for DIY home cleaners

Some people judge the effectiveness of their cleaning products by the way the room smells when they’re finished. Are you one of them?

A chemical smell does not mean a clean room. It means unhealthy indoor air—especially if the chemical is chlorine bleach.

That’s one reason more and more people are starting to make their own cleaners from non-toxic ingredients. Here are some more: DIY home cleaners cost less, they work just as well as expensive commercial cleaners that are good for only one cleaning job, they take up less cabinet space, and they generate less trash.  Continue reading

6 New Municipal Recycling Initiatives

Recycling bales

Bales of recycled plastic ready for reprocessing

When you go to look something up, you never know quite what you’ll find. If you don’t find what you’re looking for right away, you might find fascinating information you hadn’t even thought of.

I looked for statistics on recycling participation. I found recent news stories of several towns that have started, or are considering, new recycling programs.

Municipalities with good programs seek to make them better. Municipalities with mediocre programs or none at all seek to start something viable.

According to the EPA, 65% of normal trash could be recycled, but only 25% actually is. It’s a dismal figure, and only part of it can be attributed to public apathy. Some places have only recently offered recycling service at all. I suppose that means that others still have none.

Here are six new or contemplated municipal recycling programs. Continue reading

A Bottle’s Journey

Have you ever wondered what happens to your recyclables once they’re hauled away from the curb? Plastic, metal, paper and glass must be sorted and subsorted.

Many recyclable materials can never be remade into whatever they were before. They must be put to some other, and likely lower use. Many but not all. Once glass bottles have been separated from other materials, they become raw material for making new glass bottles.

The following infographic illustrates the process. Continue reading

Mushrooms or Plastic? Replacing Polystyrene Foam

EcoCradle wine shipper

EcoCradle wine shipper

What do you get when you buy something like a TV that comes in a large box? Besides the product you want, you get trash.

The bulk of that trash is a polystyrene foam, made from oil, that is mostly air and otherwise the most toxic and difficult to recycle of plastics. And very bulky. It lasts about forever, too.

I reported a couple of years ago about a company called Ecovative that grows packaging (and insulation, and automobile parts, and surfboards, and basically any other application of polystyrene foam) from mushrooms.
After you have taken your product out of the box, you can compost mushroom packaging or otherwise return it to the earth.

Here’s a TED talk given by one of the inventors, Eben Bayer. It includes a marvelous time lapse to show how the product is grown by stuffing agricultural waste, inoculated with mycelium (mushroom roots), into a mold, and then letting it sit in a dark place for a few days. Continue reading

18 Ways to Reduce Wastepaper at Home

world's largest paper wad, belatedly recycled

Minnesota’s giant paper ball, which set a Guinness record.

Do you remember the promise of the paperless society? Hah! We’re awash in paper. Not only paper for reading and writing, either.

Making paper first means cutting down trees and all the energy and transportation that requires. Then it requires a lot of water and a lot of chemicals, making lots of wastewater that has to go somewhere.

One of the easiest ways you can make a difference to the environment is to use less paper. You know the 3 Rs of recycling: reduce, reuse, and recycle. And that’s the order of importance.

Here are some ways to allow less paper in your home, and then reuse at least some of it before recycling it: Continue reading

Solar Panels on Famous Landmarks

Solar Valley Micro-E Hotel

Solar Valley Micro-E Hotel, Dezhou, China

Contributed by Stuart Amm

Renewable energy has been a topic that has generated a lot of interest in recent years. It has gained a lot of column inches in the media in terms specifically of climate change worldwide and how it will inevitably affect us all.

Also, we have unfortunately been witness to some terrifying weather pattern changes resulting in a number of related natural disasters. Weather scientists claim that this is a pattern set to continue as climate change continues to take hold.

We as individuals have the opportunity to make a difference even if it means small changes in our behaviour. Recycling more household products, choosing renewable energy options are just two things that can be done. If everyone made a small change, the world’s environment would reap the rewards.

Solar panels are one option for incorporating renewable energy into the home or business. While many may see them as off limits due to being expensive, this is actually not the case any longer with more affordable options available.

It should also be noted that in the long run, they can actually end up saving money in terms of energy costs. This StoryMap created by Half Price Shutters in Australia highlights how some of the most famous world landmarks have chosen to install solar panels. Continue reading