Electricity from heat | Combine

Electricity from heat

I have been asked to write something technical (for once). Instead of delegating to one of our more capable engineers I decided to give it a go myself. I hope there are some interesting tidbits for you to digest in the following. As my colleagues at Combine might have noticed we have been quite active lately in finding our first customers in Stockholm as well as expanding our customer base at our previously established offices. Along the way I have run into some very interesting products and services, so I am going to talk about these, or the technologies involved. Asking the guy who hasn’t done any real engineering work for many years to write a technology post is flattering. I hope the things I’ve noticed aren’t too much old news.

Electricity from heat

Well, no big news there. But how about using existing waste heat instead of burning oil or splitting atoms? Instead of superheating steam just settling for 70-120C source temperatures?
The technology is surprisingly simple, but clever. Here is some text and an image from the Climeon homepage (www.climeon.com):

The heat, from geothermal sources, industrial waste heat or power production, is fed to the Climeon unit. Inside the Climeon unit a heat exchanger transfers the heat to an internal fluid, which vaporizes due to its lower boiling point. The vapors are then expanded over a turbine to run a generator and produce electricity.

Fundamentally the same electricity generation scheme as a nuclear power plant, but no nuclear stuff.
The energy efficiency of, for instance, a nuclear plant design might be considered poor considering the amount of heat that is wasted (just cooled off for no gain). Plants that combine electricity generation and district heating are more efficient from that point of view, but perhaps transporting heat to remote districts using nuclear coolant is not a great idea.
In this case, the concept is to use heat that is already there and unused, so efficiency can instead be measured solely as the amount of electricity generated per unit of heat energy. If the source is geothermal it’s basically electricity for free, once you make your initial investment and maintenance allocations.

I think the concept is great and hope they do well.

Batteries, when they are no longer suitable for their initial purpose?

There seem to be four basic answers to this question

  1. We made our money while they worked, now we need to get rid of them at as low cost as possible
  2. We are hoping to recycle them efficiently and make use of that
  3. We are hoping someone else wants them and hopefully make use of that
  4. O boy, where did all these batteries come from?

The first answer is understandable, but not convincing from an environmental or “big picture” point of view. Established recycling technology for Lithium-Ion batteries has a couple of glaring drawbacks, mainly that it doesn’t work that well and that it is based on melting (which costs a lot of energy).

The second answer is hopeful and often based on the idea that recycling will improve. Research is underway, most promising is research based on technologies that have existed in the mining industry for over 100 years. The idea in mining is to crush the material and mix it up with fluid containing molecules that attach to the element one wishes to extract. The newly formed molecules float up to the surface of the fluid and can be skimmed off (or assume whatever property might make it easy to separate them from the fluid). Then a further stage filters out the desired element. The research is looking to do this similarly in steps, separating all the desired elements along the way.

The third answer is also hopeful. As we have discussed in previous posts, the idea of a functioning business with second and possibly third life applications for used batteries is quite dependent on buyers and sellers knowing the condition of the batteries. We are hoping to do something of our own in this area, as you know.

Unfortunately, the fourth answer does exist. I am not going to point any fingers and just leave it there.

Unless someone comes up with a better battery technology soon, we are looking at an ever-increasing need for answers 2 and 3 to win out.
Authorities are also unlikely to accept answers 1 or 4 in the long run, IMO (global perspective, visualize massive toxic junkyards in some third world country). The pressure is more likely to increase than decrease on manufacturers, and it will be interesting to see where in the value chain responsibilities land. Passing the buck will probably not be that easy without some serious documentation to show where the batteries went and who is responsible for them.

Pet project

To wind this up I am going to talk a bit about a pet project. We have been asked to demonstrate something on the theme “technology is fun” for an event (Netgroup anniversary) taking place at the Göteborg opera house.
I am going to attempt to build a plasma arc speaker. They have always caught my eye (you can look them up or watch some videos on Youtube), so even if it has already been done, I think it is a perfect fit considering the venue.

First, I would like to point out that this is a high-voltage design, so building it at home with a simple on/off switch is not a great idea if you have small (or overly curious) children running around. It can cause serious heart problems or kill you, and it produces ozone which can be lethal at concentrations of more than 50ppm. Great fun, right?

Anyway, the idea I am using is something like this

For the power source, I will use a standard 700W PC power supply, using the 12V output. This will go to the flyback transformer and switching MOSFETs.

The audio source will probably be an obsolete MP3 player. The signal will go to a 555, which will then control the switching MOSFETs (I’ll use 3 parallel STP40NF10L).

The flyback transformer has the property of being able to produce high voltages, in the X kV range. Also, instead of being fed by a DC source it is typically fed by a switched source in the XY kHz range.

My idea is to produce the arc between two stainless steel screws of some respectable dimension.

So, kV and kHz? This means we get a modulated plasma arc that can play the higher frequencies of music well. It should actually be able to do it very well, since there are no moving parts, unlike speaker membranes and similar. It won’t be very loud since I have no plans to ionize western Sweden or kill the guests at the event, but it will be fun to see if I can make it work.

If anyone feels a huge urge to fiddle around with it together with me, I am looking for someone who can prevent me from electrocuting myself and maybe has some ideas for an ozone trap.

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