Wow, so there's some interest in this topic. I've done some digging
and learned some particulars. There's an interest in home-sized and farm-sized systems among people who desire independence from "the grid" (survivalists, dairy farmers (ever tried to milk 200 cows by hand?
), people who can't get 3-phase power
, etc....).
I think the plant in Lincoln that you're referring to is called Tractebel and they've been burning tires, sawdust, woodchips and who-knows-what for a while now. They're currently trying to get their permit upped to burn more tires. I have some background in industrial turbine generators from 600KVA up to 10MVA, but for a small operation, the rules are vastly different.
Roughly speaking, assume that 1KVA = 1hp (746 watts = 1hp, but there are losses in the systems)
. So if your mill is 25hp, you need probably a 50KVA generator with a steam turbine or piston engine and a big flywheel to help your motor overcome it's startup current. Of course, there's always the option of running your mill with a steam turbine instead of an electric or gas motor, but then you have live steam in your work environment and that really increases the risk.
The key would be to keep the genset within the limits of low pressure systems (<250 psi) and to keep the heat output of the boiler below the radar for Fed and State environmental regs. Low pressure steam is much safer and less stringently regulated than high pressure. I'm not sure about this, but I think a 100 KVA system also falls just under the EPA limit. If you have employees, there's also some OSHA and other impacts.
Overall, this suggests that you could run a small mill and your household with the electricity and heat kilns, barns, homes (and even hot tubs) while condensing the turbine or engine "exhaust" (so that it can be recirculated into the boiler feedwater). Unfortunately, a 10KVA system costs about $10,000 and scaling it up to 100KVA could easily approach $50,000. Finding ways to decrease the cost or boost the efficiency of a cheaper system is something I would have to tackle.
The problem I'm hoping to find some expertise with is determining whether moving wood into the boiler would become a full time job. I wouldn't want to work full time just to be able to say goodbye to Consumers Power.
There's a logger/sawyer nearby who heats his home and a 30MBF kiln from an outdoor wood furnace that he supposedly only loads wood into once per day, but there's a big difference between letting the power company circulate the hot water and pouring in enough heat to produce a decent amount of electricity.
If anybody can conservatively estimate the heat content of a cubic foot of waste wood, I can probably track down a btu/hp ratio for steam turbines and steam engines. That would give me some handle on the scope of this.
