GENERATOR HEAT RECOVERY CONSIDERATIONS IN ARCTIC VILLAGE APPLICATIONS

LCDR William Fraser, P.E.

Alaska Native Tribal Health Consortium Division of Environmental Health & EngineeringJune 2011Who We Are

ANTHCNon-profit, statewide organization Provides a range of medical and community health services for more than 125,000 Alaska Natives. Part of the Alaska Tribal Health System, which is owned and managed by the 229 federally recognized tribes in Alaska and by their respectiveregional health organizations.

ANTHC History1970s-1990s: Regional health organizations in AlaskaPassage of P.L. 105-83 established ANTHC, the only THO established by statuteDecember 1997: ANTHC incorporated as non-profit 501(c)(3)June 1998: Initial contract with IHS.

ANTHC HistoryOctober 1998: Contract expanded to include Environmental Health & Engineering

October 1998: ANTHC becomes a P.L. 93-638 Title III Self-Governance entity, signing the Alaska Tribal Health Compact

DEHEDesigns and Constructs Health and Sanitation FacilitiesProvides operations supportMonitors & develops standards for mitigating climate change impactsHealth impact studiesEnvironmental Grants & training

Water & Sewer- Why?

What does this have to do with Heat Recovery?Hospitalizations are 5 times higher in communities w/o piped water & sewer.Typical Fuel consumption for an Arctic WTP w/ piped water & sewer: 8000-25,000 Gal / Year Fuel OilFuel Prices between $6.00 & $8.00 / Gal. and rising.Heat recovery can help make it affordable.

Extreme Climate

High Energy Use

HEAT RECOVERY FROM POWER PLANTS2 basic types: Jacket recoveryStack recoverySmall Scale: 50 KW to 3500 KWIdeal for space heat and process heatConsidered a fuel saver, not a primary source of heat.

Kwigillingok Generator Facility

ADVANTAGES OF HEAT RECOVERYVery green- reduces carbon footprint.Can dramatically increase the economic viability of a community water system.Adds additional redundancy to the building heating system.

DISADVANTAGES OF HEAT RECOVERYRequires an agreement with the power utility, often with a charge for waste heat. Usually increases the complexity of the heating system, especially in Washeterias.Requires additional maintenance and coordination between power utility and building owner.

Other Solutions

SO YOU WANT TO BE GREENWhat do you need to know before you start?Estimating available waste heatDeciding on a heat recovery strategySelecting system components

WHAT DO YOU NEED TO KNOW BEFORE YOU START?Who owns the generators and what are their conditions?Do you have a viable path between the waste heat source and the building?What type of building are you serving?Are there other buildings served by the waste heat?What type of monitoring do you want?Who is going to maintain it?

ESTIMATING AVAILABLE WASTE HEATQA =QGEN QPIPE - QO QA:Minimum available waste heat for your building

QGEN:Average generator output during peak heating season (typically much less than rated capacity) in BTUs / Hour

QPIPE:Heat loss from distribution piping during peak heating season. Typically about 50-60 BTUH / LF

QO:Heat used by other buildings on the waste heat system (sometimes this is prioritized by order of connection, so be careful)

HEAT RECOVERY RULES OF THUMB:Generator Output: 1/3 Electricity, 1/3 Jacket heat, 1/3 Stack loss1300-2000 BTU / KW-Hr (Available Jacket Heat)100,000 BTU delivered heat = 1 gallon of dieselAnnual Fuel Saved = .3 x Power plant annual fuel used x 0.6Pumping Energy Costs

BREAK EVEN TEMPERATURE DIFFERENCETBR:Break even temperature difference between Generator Heating Supply and Building Heating Return (Deg F)PPUMP:Pump power (W)CE:Electrical cost ($ / kWh)COIL:Fuel cost ($ / Gallon) (80% efficiency assumed)UAHX:Heat exchanger U factor multiplied by HX area (BTU/ Hr x Deg F)GPM:Heat exchanger glycol flow rate (GPM)

(This formula only applies in special case of counterflow HX with matching flow rates and sufficient heating demand to use all of the waste heat)TBR =PPUMP x CE x 100COIL x UAHXPPUMP x CE x 100900 x GPM x COIL+

ESTIMATING WASTE HEAT DEMANDQD =QBLG + QPROC QD:Waste heat demand (typically does not include dryers)

QBLG:Building envelope heat losses (must engineer heating system for lower temperatures than typical heating systems)

QPROC:Heat required by process systems (includes circulation loops, raw water heat add, storage tanks, etc. This is where waste heat really shines)

SELECTING A HEAT RECOVERY STRATEGYDirect heat add to potable water:Double wall shell and tube, independent of boiler system (Kiana)Small system with single boiler:Pipe heat exchanger in series with boiler (Chenega Bay)Large system with multiple boilers:Pipe heat exchanger in primary / secondary arrangement (Kwigillingok)

GENERATOR HEAT RECOVERY ARRANGEMENT

RECOVERED HEAT INTO POTABLE WATER

HEAT EXCHANGER IN SERIES WITH BOILER

PRIMARY / SECONDARY HEAT EXCHANGER DIAGRAM

Minto Heat Recovery

WASTE HEAT CONTROLLERTurns on at 8 Deg F differenceTurns off at 4 Deg F differenceBuilt in HOA switch.Provides 1p/2t switch which can handle a 1 HP pump.

BTU METER

Plate / Frame Heat Exchanger

Brazed Plate Heat Exchangers

Shell & Tube Heat Exchangers

Typical pumps

AMOT Valve

DESIGN COMMENTSUse Brazed Plate or Plate / Frame heat exchangers Provide controls to ensure heat is not transferred back to generator cooling system.Provide controls to minimize electric power consumptionProvide BTU monitoring if being billed by local utilityProvide pressure relief on pipelineProvide strainers on both sides of heat exchanger (reduces cleaning of heat exchanger).Provide air separator on pipeline side of system.Provide glycol system monitoring and makeup.Provide expansion compensationDont use HDPE pipe. Copper, Steel, PEX, Stainless steel.Monitor pipeline for leaks and pressure.

Questions?

****An example: AVEC charges 30% of offset fuel cost, electricity is $0.20 / KWH (PCE price), Fuel is $7.00 / Gal, Pump power is 850W

TBR = *****