Storing electricity as heat! It's so, uh, hot right now. I talk with the head of a company that makes a thermal battery that outputs either heat or electricity. It's one of my favorite technologies around -- super-geeked about this one.
Captivating interview, very well done both parts! Just to widen knowledge of listeners, we at Silbat (www.silbat.com) in Madrid, Spain, are doing similar things, but instead of graphite blocks we store electricity (again using resistors to convert to heat) in the latent heat of fusion of metal grade Si. Silicon is the 2nd most abundant element on the Earth's crust and has the 2nd highest latent heat of fusion. Besides, we operate at a constant temperature, 1414C, the melting point of Si. As Antora, we retrieve the electricity (discharge) using TPV cells and have recently produced our first TPV module. In our case, we target a 40' shipping container as the modular final product housing, containing something in the range of 100kW/100hrs. According to MIT's Trancik Lab, fully dispatchable renewables, competitive with fossil-fueled power plants, require storage backing of less than $20/kWh, energy-related CAPEX; we believe we can do it for less than $10/kWh.
Fascinating podcast, Dave, and great questions. But I wished you asked one basic question: what's the capacity of such a battery in terms of MWh, and what's the size?
Also, I literally cringed when I heard you say, "you can buy renewable energy by buying RECs." No, Dave. You can buy a piece of paper when you buy RECs, not renewable energy. Later, you redeemed yourself by replacing "RECs" with "hourly RECs". Ok, all's forgiven. For now.
It sounds simple but to come up with the final block of carbon with the correct purity, thermal conductivity and shape did require a lot of engineering. The testing of the carbon at different temperatures to find that at >2,000 degC it emits light was such exciting work. Acheiving a 40% efficient single junction thermal p.v. cell by reflecting unused photons back to the carbon, is off the charts as far as the present 23% max efficient solar cells.
What is the temp of the cooling water discharge for the water used to cool the reflective mirror that returns the photons to the core of the unit? Would it be hot enough and abundant enough to provide district heating or some other lower temp process heat (heat greenhouses?)?
Graphite at those temperatures necessitates a controlled atmosphere (else it escapes as CO₂ and CO). So where Rondo has to worry about fracture on rapid changes in stored capacity, Antora has to worry about springing an air leak and the whole thing converting into CO₂ (burning). This suggests putting the radiative conversion inside the controlled atmosphere envelope, which turns this into a space-like application where servicing is a PITA, if possible at all, during operation. Doing the full discharge for service brings back the Rondo challenge, it won't be the thermal mass breaking but the container you are holding it in that will suffer for the thermal cycle. You could have a sapphire window/shutter but that'll start to creep above 1500C. I guess you could catch and re-emit the useful photons outside the bubble with a tailored conduit/rod piercing the shell (preferentially emitting light at the wavelength preferred by your cell). Otherwise you are either inside the bubble of contained atmosphere and potentially quite warm, or outside the bubble and serviceable. A very interesting concept to be sure, and quite sensible to be working in pure thermal mass mode for the first to market example.
At those operating temperatures there is a lot of co-generation potential if the industrial use you bootstrapped the project with becomes less viable after the interconnect to the grid has finally been provided (e.g. one will have options to move to pure grid-power softening if the initial industrial demand evaporates).
Captivating interview, very well done both parts! Just to widen knowledge of listeners, we at Silbat (www.silbat.com) in Madrid, Spain, are doing similar things, but instead of graphite blocks we store electricity (again using resistors to convert to heat) in the latent heat of fusion of metal grade Si. Silicon is the 2nd most abundant element on the Earth's crust and has the 2nd highest latent heat of fusion. Besides, we operate at a constant temperature, 1414C, the melting point of Si. As Antora, we retrieve the electricity (discharge) using TPV cells and have recently produced our first TPV module. In our case, we target a 40' shipping container as the modular final product housing, containing something in the range of 100kW/100hrs. According to MIT's Trancik Lab, fully dispatchable renewables, competitive with fossil-fueled power plants, require storage backing of less than $20/kWh, energy-related CAPEX; we believe we can do it for less than $10/kWh.
Fascinating podcast, Dave, and great questions. But I wished you asked one basic question: what's the capacity of such a battery in terms of MWh, and what's the size?
Also, I literally cringed when I heard you say, "you can buy renewable energy by buying RECs." No, Dave. You can buy a piece of paper when you buy RECs, not renewable energy. Later, you redeemed yourself by replacing "RECs" with "hourly RECs". Ok, all's forgiven. For now.
James L.
It sounds simple but to come up with the final block of carbon with the correct purity, thermal conductivity and shape did require a lot of engineering. The testing of the carbon at different temperatures to find that at >2,000 degC it emits light was such exciting work. Acheiving a 40% efficient single junction thermal p.v. cell by reflecting unused photons back to the carbon, is off the charts as far as the present 23% max efficient solar cells.
I love it when David gets excited about energy tech. His enthusiasm is infectious!
What is the temp of the cooling water discharge for the water used to cool the reflective mirror that returns the photons to the core of the unit? Would it be hot enough and abundant enough to provide district heating or some other lower temp process heat (heat greenhouses?)?
Graphite at those temperatures necessitates a controlled atmosphere (else it escapes as CO₂ and CO). So where Rondo has to worry about fracture on rapid changes in stored capacity, Antora has to worry about springing an air leak and the whole thing converting into CO₂ (burning). This suggests putting the radiative conversion inside the controlled atmosphere envelope, which turns this into a space-like application where servicing is a PITA, if possible at all, during operation. Doing the full discharge for service brings back the Rondo challenge, it won't be the thermal mass breaking but the container you are holding it in that will suffer for the thermal cycle. You could have a sapphire window/shutter but that'll start to creep above 1500C. I guess you could catch and re-emit the useful photons outside the bubble with a tailored conduit/rod piercing the shell (preferentially emitting light at the wavelength preferred by your cell). Otherwise you are either inside the bubble of contained atmosphere and potentially quite warm, or outside the bubble and serviceable. A very interesting concept to be sure, and quite sensible to be working in pure thermal mass mode for the first to market example.
At those operating temperatures there is a lot of co-generation potential if the industrial use you bootstrapped the project with becomes less viable after the interconnect to the grid has finally been provided (e.g. one will have options to move to pure grid-power softening if the initial industrial demand evaporates).