GENERATOR HEAT RECOVERY CONSIDERATIONS IN ARCTIC

VILLAGE APPLICATIONS

LCDR William Fraser, P.E.

Alaska Native Tribal Health Consortium Division of Environmental Health & Engineering

June 2011

Who We Are

ANTHC Non-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 respective regional health organizations.

ANTHC History

1970s-1990s: Regional health organizations in Alaska

Passage of P.L. 105-83 established ANTHC, the only THO established by statute

December 1997: ANTHC incorporated as non-profit 501(c)(3)

June 1998: Initial contract with IHS.

ANTHC History

October 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

DEHE

Designs and Constructs Health and Sanitation Facilities

Provides operations support Monitors & develops standards for

mitigating climate change impacts Health impact studies Environmental 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 Oil

Fuel 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 PLANTS 2 basic types:

Jacket recoveryStack recovery

Small Scale: 50 KW to 3500 KW Ideal for space heat and process heat Considered a fuel saver, not a primary

source of heat.

Kwigillingok Generator Facility

ADVANTAGES OF HEAT RECOVERY Very 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 RECOVERY Requires 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 GREEN

What do you need to know before you start?

Estimating available waste heat Deciding on a heat recovery strategy Selecting 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 HEAT

QA = 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 loss 1300-2000 BTU / KW-Hr (Available Jacket Heat) 100,000 BTU delivered heat = 1 gallon of diesel Annual Fuel Saved = .3 x Power plant annual

fuel used x 0.6 Pumping Energy Costs <= 10% Fuel Value

BREAK EVEN TEMPERATURE DIFFERENCE

TBR: 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 100

COIL x UAHX

PPUMP x CE x 100

900 x GPM x COIL

+

ESTIMATING WASTE HEAT DEMAND

QD = 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 STRATEGY Direct 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 CONTROLLER

Turns on at 8 Deg F difference

Turns off at 4 Deg F difference

Built 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 COMMENTS Use 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 consumption Provide BTU monitoring if being billed by local utility Provide pressure relief on pipeline Provide 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 compensation Don’t use HDPE pipe. Copper, Steel, PEX, Stainless steel. Monitor pipeline for leaks and pressure.

Questions?