Fastest Paybacks 3

[friartuck]

We are constantly being pressured into 'going green' and providing the best efficiency systems.

I was recently pressured into using solar panel heating for hot water generation. On the same job there was a request for PV cells tp generate electricity for a similar use. Paybacks for these systems was estimated at over 100 years Due to site conditions and climate etc)

I don't mind using energy saving products such as static recuperators and run around coils so long as there is a reasonable payback and that the equipment is sufficiently robust and reliable to make its use a feasible proposition to the client.

What devices or systems give the best payback?

PS I work in the heating, ventilation and air-conditioning industry working with boilers, fans, chillers, controls etc.

Friar Tuck of Sherwood

 

[zdas04]

Friar,
The only "Green" technology I've ever come across that made any real-world economic sense is waste-heat recovery (e.g., co-gen). At today's energy prices and projections of price forecasts, your 100 year payout is pretty common for the passive solar projects I've seen. I've looked at solar hot water (for tank heaters on wellsites), solar PV system to run pumps (the Oil company I worked for was the worlds largest producer of solar PV systems), and wind. We use thousands of PV panels to charge batteries in remote SCADA systems, but the economics of using them for a motor load didn't work.

Some of the fuel cells coming on the market that use methane (often doped with CO2) without the need to generate H2 before hand are pretty attractive if you can use the huge heat load. In HVAC, I'd be looking at those sorts of fuel cells and use the waste heat for domestic hot water, thermal-mass heating systems, etc. Total system return on capital can sometimes even be as good as a passbook account (a couple of projects I looked at almost made 3% return on capital and a 20 year payout, unfortunately our hurddle rate for "green projects" was 8%, it was 25% for profit-producing projects).

The driving force behind solar water-heating has always been emotion, never hard-headed economics. You won't find a passive solar water heater that can approach a modern water heater at gas prices under $600/therm (current prices are closer to $60/therm). The new on-demand water heaters will still beat solar at $1,000/therm.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The Plural of "anecdote" is not "data"

 

[buzzp]

You must not forget the most economical 'green' heating and cooling system, geothermal!

 

[quark]

Back pressure turbine can be one option.

 

[Cooky]

Friar,

In the UK, the absorption chiller has the potential for 'going green'. They can be used as part of a CHP (combined heat & power) system, they use the waste heat generated by engines that power generator sets. I've used these successfully on several projects, to supply chilled water and hot water. For these systems to be effective, you need an application that requires a constant heating and cooling load. Don't forget that these systems are eligible for UK government ECA (enhanced capital allowance)
tax rebate.

Here's another idea. Assuming you have a constant cooling and domestic hot water demand, you can use a water-to-water heat pump chiller to remove energy from the chilled water and add this energy to a DHW system. I have used the Carrier 30HXC chiller to achieve this, as it operates with condenser water temperatures of up to 63 deg.C (I work for Carrier).

Cooky.

 

[jmw]

Particularly relevant to you, Friartuck, would be the ice slurry research which should to pay dividends in cooling systems, chillers and cold storage facilities.
The alcohol and water approach seems good to me but I understand the Japanese favour a normal water system if they can keep the ice grains from clumping.
The Danish Energy Institute is involved in this.

http://www.muel.com/products/thermalstorage/docs/ore/default.htm

http://www.iea-dhc.org/dhc_III6a.htm

http://www.techtransfer.anl.gov/highlights/9-3/iceslurry.html

http://www.et.anl.gov/sections/te/research/ice_slurries.html

JMW

http://www.viscoanalyser.com

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[friartuck]

I used to work for a ventilation/air-conditioning/controls orientated company who made 'demand ventilation'. The fans were speed controlled based on co2 or temperature.

The claims were that 40% savings were possible though I never saw any real proof. Does anyone have such a system that has been up and running for a while that has also been monitored?

If 40% savings were realsitic, then I suppose this would have really fast paybacks.

Are there any other fast payback systems that a client would drool over, or are we in general always looking at
5-7 years plus before payback.

Most clients don't seem to be interested unless they can see immediate savings.

Friar Tuck of Sherwood