wood pellet boiler running organic rankine cycle power plant?

would this be a profitable business to run a few wood pellet industrial sized boilers that heat water to 180 degrees that will be pumped to a lot of organic rankine cycle electric power generators? the electricity would be sold to the grid. also there could be a large compost pile of wood chips with a coil running through the pile to heat the water up to 180 degrees so the pellet boilers would not have to run all the time. solar photovoltaic would be used to power the low energy requirement for the boilers and circulator pumps and controls. i know they have sustainable woody biomass power plants that run on wood pellets and chips but wanted a second opinion. the difference between my idea and the working models is that my idea does not use steam but just hot water.

My first question would be how does your electric company feel about buying power from small producers? For me, they are required to do net-metering, but only up to the limit of what I use in a year. Since that amounts to about $360, there is no way it could be 'profitable' (though it could of course be worthwhile).

In other words, I would recommend that you figure out how to make a profit selling electricity at all, before thinking about what system to use to generate it.

Wesley johnsen wrote:would this be a profitable business to run a few wood pellet industrial sized boilers that heat water to 180 degrees that will be pumped to a lot of organic rankine cycle electric power generators? the electricity would be sold to the grid. also there could be a large compost pile of wood chips with a coil running through the pile to heat the water up to 180 degrees so the pellet boilers would not have to run all the time. solar photovoltaic would be used to power the low energy requirement for the boilers and circulator pumps and controls. i know they have sustainable woody biomass power plants that run on wood pellets and chips but wanted a second opinion. the difference between my idea and the working models is that my idea does not use steam but just hot water.

No. The main problem is the high initial cost combined with the very low overall efficiency in generating the electricity. If you desire to use wood to generate electricity, then the only viable system is a wood gas engine system. Small rankine cycle engines (organic working fluid or steam) will not be viable for primarily generating electricity, but might be suitable where heat is the primary desired product. A sophisticated modern steam engine system might be a different story, but these are not commercially available.

For more information, I recommend you research wood gas engine systems at www.gekgasifier.com and www.driveonwood.com. A fairly large and fairly simple wood gas engine system can be surprisingly efficient at generating electricity when the system is operated under optimal conditions. The larger systems will not only be more efficient, but they can also use fairly large wood chunks (like baseball size) which will lessen the fuel processing requirements of the system. If your goal is to feed the grid, then you're going to need high power along with a helluvalotta wood to be profitable. Wood pellets are a non-starter as they are too expensive. You need access to copious amounts of raw wood resources along with an efficient system of processing the wood fuel for use in the system. Use the heat from the system to dry the fuel.

There are large industrial wood gas engine systems manufactured by Jenbacher. There is a person active on the forum who claims to have experience with these systems. You might contact him (r john) for information.

Marcos Buenijo wrote:If you desire to use wood to generate electricity, then the only viable system is a wood gas engine system.

That's quite an assertion. Do you have examples (positive and negative) to provide?

Topher Belknap wrote:

That's quite an assertion. Do you have examples (positive and negative) to provide?

Sure. First, note that my argument has several restrictions. Since the OP emphasized selling electricity, then I have not considered the value of "waste heat" for anything other than perhaps wood fuel drying. Also, I am not considering a very large scale that might allow for using highly efficient modern steam power hardware (such as large multi-staged heat regenerative turbine systems). In my opinion, the fuel consumption rates would be too high to support such a system economically.

Basically, my position boils down to considering the most economical alternative at the targeted setting. There exist commercial wood gas engine systems at the low megawatt outputs that can generate electricity at an overall efficiency on the order of 30% (see Jenbacher). There are also small scale units on the order of 100 KW that show 20%+ overall efficiency (google will find them). I know of no commercial steam power system at the targeted scale that can compete with respect to initial and ongoing costs (of which efficiency is a paramount consideration)- with one notable exception. A new company (Terrajoule) has brought back a proven steam engine design known for high efficiency and extreme reliability (the Skinner Universal Uniflow). While designed for solar thermal with thermal storage, this system could generate electricity at a rate of several hundred KW with biomass fuel at an overall efficiency of 20%+. The ability to avoid many gas processing steps combined with the simplicity and extreme reliability of the system should make it a winner in this application.

In short, it's mostly the general lack of steam power hardware suitable for the application that causes me to favor internal combustion.

Marcos Buenijo wrote:

Topher Belknap wrote:

That's quite an assertion.

In short, it's mostly the general lack of steam power hardware suitable for the application that causes me to favor internal combustion.

Which strikes me as a far more reasonable assertion.

Thank You Kindly,
Topher