David, Heat rates were calculated the American way, using HHV. :-)
Steam and ORC was proposed in different configurations. A couple of companies proposed using backpressure turbines or steam engines with oil heated from the exhaust to drive an ORC turbine. Other proposed hot oil boilers and ORC turbines. The 20% efficiency of Turboden and others is 20% of the heat input to the turbine so you have to subtract the efficiency of converting the wet wood fuel to hot oil which runs from 62-72% of HHV depending on the MC of the fuel and the boiler configuration. Now since you have 70% of the heat input exiting the ORD as waste heat you need to dump it to a heat consumer. That work fine if you have an onsite heat consumer or district heat arrangement. Unfortunately most of our American towns are not laid out so conveniently that we can afford to build a district heat system for a small biomass plant. I agree that for all the literature on ORC there are very few head to head comparisons with steam of CAPEX and OPEX. The manpower and capital requirements are pretty similar for both the steam and ORC systems because of safety and other considerations. In the end the levelized cost of electricity (LCOE) will be higher for the ORC if you don't have a heat customer. If your need is primarily heat , or if you have waste heat available, the ORC systems look great. A new 2 MWe plant on Vancouver island with a PW/Turboden ORC uses oil from an existing hot oil boiler at a wood plant. There are many more hot oil systems in use in Canada than in the US. We have had varied experience with hot oil here. Tom -----Original Message----- From: Gasification [mailto:[email protected]] On Behalf Of David Coote Sent: Friday, February 01, 2013 3:26 PM To: [email protected] Subject: Re: [Gasification] Gasification Digest, Vol 30, Issue 1: ORC, gasifier, SRC systems at around the 2MWe level Hi Tom, I'm doing a bit of work in this space at the moment. How did you define Btu's below for the Btu/kWh efficiency calculation? Was it from the HHV or LHV of the original biomass fuel? When you say steam + ORC is that off an existing boiler? The ORC vendors claim that you can get 20% electrical efficiency at the 2MWe system level using a biomass system heating thermal oil that would run at much lower temperatures and pressures than a similar SRC system. Hence cheaper operations and maintenance costs. I haven't managed to find data yet on the cost delta between thermal oil biomass systems and the more common biomass systems heating water/steam. Regards David On 2/02/2013 7:00 AM, [email protected] wrote: > Message: 20 > Date: Fri, 1 Feb 2013 09:04:09 -0800 > From: "Tom Miles"<[email protected]> > To: "'Discussion of biomass pyrolysis and gasification'" > <[email protected]>, "'stuart mather'" > <[email protected]> > Subject: Re: [Gasification] mycoremediation of tarry water > Message-ID:<[email protected]> > Content-Type: text/plain; charset="us-ascii" > > Except . . apparently when you do a detailed engineering feasibility > study and get quotes from suppliers. In a recent 2 MWe project we > found that gasifiers were 50% higher in capital cost than steam > (turbines or engines) or steam + ORC. In the opinion of a couple of > gasifier suppliers, for our economic circumstances, gasifiers could be > more competitive in the 5 to 10 MWe scale. At 10 MWe steam becomes > more economic. We were interested to see that at the 2 MWe scale steam > or steam + ORC could be competitive. There are about 200 ORC systems > in operation on biomass but to use ORC you need a use for large amounts of low quality heat. > > > > We found that while a 5-10 MWe biomass plant may have a heat rate > (fuel to > power) of 14,500 Btu/kWh, the efficiency for the 2 MWe plant ranged > from > 18,500-22,800 Btu/kWh for small scale steam turbines; 28,000-55,000 > Btu/kWh for ORC boiler-turbines and 24,000 Btu/kWh for gasifiers. In > this 2 MWe case gasification did not demonstrate an advantage in > capital and operating costs or fuel to power efficiency compared with steam or steam + ORC. > > > > Tom > > _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenerg ylists.org for more Gasifiers, News and Information see our web site: http://gasifiers.bioenergylists.org/ _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org for more Gasifiers, News and Information see our web site: http://gasifiers.bioenergylists.org/
