[Gasification] Gasification Digest, Vol 30, Issue 1: ORC, gasifier, SRC systems at around the 2MWe level

[Tom Miles]

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:gasification-bounces at lists.bioenergylists.org] On
Behalf Of David Coote
Sent: Friday, February 01, 2013 3:26 PM
To: gasification at lists.bioenergylists.org
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, gasification-request at lists.bioenergylists.org wrote:
> Message: 20
> Date: Fri, 1 Feb 2013 09:04:09 -0800
> From: "Tom Miles"<tmiles at trmiles.com>
> To: "'Discussion of biomass pyrolysis and gasification'"
> 	<gasification at lists.bioenergylists.org>, 	"'stuart mather'"
> 	<kneebraceboy at yahoo.com.au>
> Subject: Re: [Gasification] mycoremediation of tarry water 
> Message-ID:<00b601ce009e$27e317b0$77a94710$@trmiles.com>
> 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
>
>    


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