eventually we would hope to get there, but, we are trying to have an edge somewhere that isn't the literal most refined and large capex part of the market first. if we can have a 10x edge
oxygen works and might be worth it for a stationary application like a powerplant for an AI data center. but NOx breaks down exothermically. so our approach if you hold the flame at >1300 C for less than a second or so you can destroy most of the NOx. This doesn't happen in a Diesel because the pulse stays that hot for only a short time, locking in the NOX that is produced. this is a matter of sizing the heat exchanger / flow rates correctly. we have to validate all this though. good question
fuel cells have trouble being cheap, lightweight, high efficiency, and long lasting, all at the same time. I think this could have better scaling on all those dimensions, plus could use natural gas or propane or other fuels for when you don't have hydrogen
we don't see any degradation in sapphire tubes, though quartz, which is more convenient to work with because it almost completely resists thermoshock, does degrade slowly. there is a layer of salt on the tube which becomes transparent when melted, above 800 C. sodium vapor is provided to the reaction tube via direct evaporation -- melted sodium has a high surface tension and surface affinity for alumina, and wicks into the chamber. after combustion as it cools, it reforms into sodium chloride. for all fuels we've explored, sodium-chlorine is the maximum bond energy, but you can have some swaps if you have for some reaction alkali or fluorine in your fuel (don't!), the sodium chloride condenses from 800-1400C in the heat exchanger, and then wicks itself back along the surface to where it is evaporating. We hope to drive this process to some number of 99.99..% recovery, and just add granular salt (or could be a solution) to replenish. There is only a few % of salt needed in the flame, and if you recover 99.9% of the salt then you would have hundreds of total refuelings before you need to replenish a salt vessel of about 1%.
that's correct. the mass of the power related systems are a moving target based on what we're developing. but we are aiming for a medium term target of > 1 kW / kg for e.g. DC power to a drone or a hybrid drone power system
we're not aiming to break records with the absolute heat exchanger efficiency, which can get into the high 90s (%) if you're willing to devote a lot of space and mass, but we are innovating in the heat exchanger area. to capture more of the waste heat up to a higher temperature, and preheat the incoming air and possible fuel to a higher temperature, we have to exceed 1000 C and want to drive towards the 1600-1800C maximum working temperature of the high alumina 3d printed material we're using. Thankfully Formlabs has already done some of the preliminary development on the material, but it's bleeding edge both as a material and in use in heat exchangers.
you need at least valves/regulators, but for self pressurized fuels like propane, butane, or even natural gas (CNG or LNG) you can probably get away with only that, and fans for air intake and cell cooling.
fuel cells have trouble being cheap, lightweight, high efficiency, and long lasting, all at the same time. I think this could have better scaling on all those dimensions, plus could use natural gas or propane or other fuels for when you don't have hydrogen
indeed yes; the sodium is added as sodium chloride. in molten form, it wicks along sapphire and alumina surfaces, similar to a candle. it reforms into sodium chloride as the temperature drops below its boiling point -- 1400 C.
we're exploring fully sealed experiments, but, you have to get the heat into the sealed cell somehow.
maybe so. i don't know about attritable for the first applications though. may long range or duration oversight. a large % of the cost is these specialty cells which have not been scaled up to mass production. in the denominator is the intensity of light we can produce, which is based on how high a temperature we can drive, there's a very nonlinear brightness vs temperature. but at 100 suns or so we can get near to $1/W on the cells at startup scale
thanks to curl-up who posted this, whoever you are.
since it came up, "wire-to-wire" efficiency is what I intended to coin a synonym for electrical to electrical efficiency, with hydrogen storage. for example, an 80% electrical to hydrogen efficiency, and a 50% hydrogen to electrical efficiency, would yield a 40% wire to wire (electrical to electrical) efficiency. of course, people are working on 95% electric to hydrogen efficiency, and 50% fuel to electrical efficiency is a target.