Interesting, I used to review new technology under NDAs for various parties. Since the power module is a "black box", its a bit hard to see how the numbers will work out. It looks to be a thermal process, so Carnot cycle efficiency sets the maximum energy that can be captured and with such low temperature differentials, it is going to be low. Add in organic working fluids with high boiling points like the ORC folks do in Europe, and the Carnot efficiency goes up but it adds complexity and needs a custom heat exchanger. Super critical CO2 tech allows higher source temps also but requires a custom heat exchanger. In all cases Carnot efficiency is the absolute best case with no losses.
Just to see back of the envelope numbers, assume 180 F inlet, convert to degrees R (absolute) =640 R and assume the heat dump is 30 F = 490 R. Using Carnot's theorem (Th-Tc)/Th= max efficiency of 23%. If I look at ORC, I think they have an expensive working fluid that can go up to 400F so assume an inlet temp of 380F or 840R and eff pops up to 41%. Sticking with water I will be generous and assume 75% efficiency of the equipment or 17% conversion of BTU input to electrical output. I will assume 20% dry wood at 7000 BTU/lb. One KW equals 3400 BTU, so it would take 20,000 Btu input at 17% conversion efficiency. The boiler is not 100% efficient and I will swag in 70%, probably lower if its an OWB. Using 70% that is 28500 btu or about 4 pounds per hour of wood. So 10 pounds of wood/hr inlet for 1 KWhr is in the realm of possible.
My prior employer had some experience testing the Pratt &Whitney ORC units targeted for a low temp geothermal field in the SW about 10 years ago, that project went belly up. P&W had a R&D ORC unit at Chena Hot Springs in Alaska and one in CT but that was about it, they ended up selling to Turboden in Italy. I think a Japanese firm bought the rights. They were basically an air conditioning cycle running backwards with a custom "turbine/generator". Here is a business lead, I really wanted to add ORC to landfill gas engines, these are large natural gas engines in the MW range that burn cleaned up landfilll gas and convert it to electric power, they get lets of tax credits as the power is regarded as "renewable" and I think they are also tied in with the RIN market so if they can get bit more power out of the package they are interested. Those engines just sit out next to a landfill and exhaust a big chunk of the waste heat into the air at 400 degrees plus dump a pretty good amount out the radiator (around 225 F). Install a waste heat recovery unit for your working fluid on the exhaust and use the coolant through a heat exchanger as an economizer on the return water and it sure beats an OWB. Cat seems to own the market selling these engines and I think they even looked at ORC at one point as I saw some documentation at one point that they might offer it as an option. I think when P&W got out no one really picked it up. The one caveat is CAT and other engine companies hate backpressure on their engine exhausts. In another project that cannot be named we were going to tie multiple engines into a common header with an ID fan on the tail end so the engine folks could not complain about backpressure. Crypto right now is reportedly building bit coin mining equipment that is supplied power from burning waste methane from oil fields too far from the gas grid, no doubt they might want a bit more power as there is no value in the waste heat the engines generate.
The promo materials remind me of what I have seen with various sterling cycle units. Different tech but same market but there are some echos of the STM technology that started out as a car engine but switched into a waste gas engine before they went bankrupt about 15 years ago. They were based out of Michigan but very little info out there on the web. Its a niche that many have tried to fit in and no one out there has succeeded.
Most of the tech out there I reviewed over the years was tough to scale down in size, various firms built small R&D units as that was all they could afford but scaling was tough especially with turbine based tech. If your firm can commercialize the tech and make it affordable and reliable there is definitely a market but not so sure wood burners is that market.
Just to see back of the envelope numbers, assume 180 F inlet, convert to degrees R (absolute) =640 R and assume the heat dump is 30 F = 490 R. Using Carnot's theorem (Th-Tc)/Th= max efficiency of 23%. If I look at ORC, I think they have an expensive working fluid that can go up to 400F so assume an inlet temp of 380F or 840R and eff pops up to 41%. Sticking with water I will be generous and assume 75% efficiency of the equipment or 17% conversion of BTU input to electrical output. I will assume 20% dry wood at 7000 BTU/lb. One KW equals 3400 BTU, so it would take 20,000 Btu input at 17% conversion efficiency. The boiler is not 100% efficient and I will swag in 70%, probably lower if its an OWB. Using 70% that is 28500 btu or about 4 pounds per hour of wood. So 10 pounds of wood/hr inlet for 1 KWhr is in the realm of possible.
My prior employer had some experience testing the Pratt &Whitney ORC units targeted for a low temp geothermal field in the SW about 10 years ago, that project went belly up. P&W had a R&D ORC unit at Chena Hot Springs in Alaska and one in CT but that was about it, they ended up selling to Turboden in Italy. I think a Japanese firm bought the rights. They were basically an air conditioning cycle running backwards with a custom "turbine/generator". Here is a business lead, I really wanted to add ORC to landfill gas engines, these are large natural gas engines in the MW range that burn cleaned up landfilll gas and convert it to electric power, they get lets of tax credits as the power is regarded as "renewable" and I think they are also tied in with the RIN market so if they can get bit more power out of the package they are interested. Those engines just sit out next to a landfill and exhaust a big chunk of the waste heat into the air at 400 degrees plus dump a pretty good amount out the radiator (around 225 F). Install a waste heat recovery unit for your working fluid on the exhaust and use the coolant through a heat exchanger as an economizer on the return water and it sure beats an OWB. Cat seems to own the market selling these engines and I think they even looked at ORC at one point as I saw some documentation at one point that they might offer it as an option. I think when P&W got out no one really picked it up. The one caveat is CAT and other engine companies hate backpressure on their engine exhausts. In another project that cannot be named we were going to tie multiple engines into a common header with an ID fan on the tail end so the engine folks could not complain about backpressure. Crypto right now is reportedly building bit coin mining equipment that is supplied power from burning waste methane from oil fields too far from the gas grid, no doubt they might want a bit more power as there is no value in the waste heat the engines generate.
The promo materials remind me of what I have seen with various sterling cycle units. Different tech but same market but there are some echos of the STM technology that started out as a car engine but switched into a waste gas engine before they went bankrupt about 15 years ago. They were based out of Michigan but very little info out there on the web. Its a niche that many have tried to fit in and no one out there has succeeded.
Most of the tech out there I reviewed over the years was tough to scale down in size, various firms built small R&D units as that was all they could afford but scaling was tough especially with turbine based tech. If your firm can commercialize the tech and make it affordable and reliable there is definitely a market but not so sure wood burners is that market.
