Geothermal Heat Pumps in Agricultural Applications

Transcription

1 Geothermal Heat Pumps in Agricultural Applications Oregon Geothermal Working Group Meeting May 17, 2006 Alternative Farming Center, Johnson County, Tennessee Andrew Chiasson Geo-Heat Center Oregon Institute of Technology

2 Presentation Outline Overview of geothermal heat pump (GHP) systems aka: GeoExchange (GX), ground-source, ground-coupled Feasibility of agricultural applications Detroit, MI Greenhouses Ice Arena, B.C. Aquaculture Dairy farming Example agricultural installations

3 Overview: What do GHP systems provide? Heating Cooling Hot water Humidity control Ice making but also Residential Heat Pump Energy efficiency Decreased maintenance Decreased space needs Low operating costs No outdoor equipment (no noise or outdoor maintenance) Comfort & air quality Lowell, MA Reduced peak electrical loads for air conditioning

4 Components of GHP Systems 1. Earth connection Closed-loop Open-loop 2. Water-source heat pump 3. Interior heating/ cooling distribution subsystem Forced air Radiant 3 2 1

5 Components: Water-Source Heat Pump Water-to to-air or water-water heat pump ¾ to 10 ton units are most common

6 Vertical Closed-Loop Historic building in downtown Detroit, MI

7 Horizontal Closed-Loop Trenching Excavation for a horizontal ground heat exchanger Spiral slinky,

8 Open-Loop

9 Some GHP Design Considerations: Loop Sizing Closed-loop loop lengths depend on: Peak hourly load Annual heating loads vs. annual cooling loads Optimum loop lengths occur when annual loads are balanced Open-loops: Required groundwater flow rate depends on its temperature (usually about 2 gpm/ton) Groundwater quality and regulations!!

10 Some GHP Design Considerations: Peak vs. Annual Loads 1.0 % of Total Annual Load Handled % of Peak Load Installed as Geothermal Boston Dallas Denver Seattle

11 $2.00 $1.75 $1.50 $1.25 $1.00 $0.75 $0.50 GHPs and Greenhouses: Feasibility Closed Loop Installation Cost ($/m of vertical bore) Open Loop Installation Cost ($100/kW) $15 $20 $25 $30 $35 $40 $1.0 $1.5 $2.0 $2.5 $0.70 Region where geothermal could handle 15-30% of the total annual load Region where geothermal could handle 50-70% of the total annual load Region where geothermal could handle <15% of the total annual load Region where geothermal could handle 30-50% of the total annual load I N F E A S I B L E R E G I O N $4 $5 $6 $7 $8 $9 $10 $11 $12 Closed Loop Installation Cost ($/ft of vertical bore) $2 $3 $4 $5 $6 $7 $8 $9 $10 Open Loop Installation Cost ($100/ton) Natural Gas Cost ($/therm) Natural Gas Cost ($/m^3) Region where geothermal could handle up to 30% of the total annual load $0.60 R e g i o n w h e r e g e o t h e r m a l c o u l d h a n d l e >9 0 % o f t h e t o t a l a n n u a l l o a d $0.50 $0.40 Region where geothermal could handle 70-80% of the total annual load Region where geothermal could handle 80-90% of the total annual load $0.30 Region where geothermal could handle 50-70% of the total annual load Region where geothermal could handle 30-50% of the total annual load $0.20 Contours represent fraction of geothermal capacity to the peak hourly heating load Full article available at

12 R e g i o n w h e r e g e o t h e r m a l c o u l d h a n d l e > 8 0 % o f t o t a l a n n u a l l o a d Natural Gas Cost ($/therm) Natural Gas Cost ($/m^3) $2.00 $1.75 $1.50 $1.25 $1.00 $0.75 $0.50 GHPs and Aquaculture: Feasibility Closed Loop Installation Cost ($/m of vertical bore) Open Loop Installation Cost ($100/kW) $15 $20 $25 $30 $35 $40 $1.0 $1.5 $2.0 $2.5 $0.70 Region where geothermal could handle 55-80% of total annual load Region where geothermal could handle 30-55% of total annual load Region where geothermal could handle 15-30% of total annual load Region where geothermal could handle <15% of total annual load I N F E A S I B L E R E G I O N $0.60 $0.50 R e g i o n w h e r e g e o t h e r m a l c o u l d h a n d l e $0.40 > 9 0 % o f t o t a l a n n u a l l o a d Region where geothermal could handle 80-90% of the total annual load $0.30 Region where geothermal could handle 55-80% of the total annual load Region where geothermal could handle 30-55% of the total annual load $0.20 Region where geothermal could handle up to 30% of the total annual load $4 $5 $6 $7 $8 $9 $10 $11 $12 Closed Loop Installation Cost ($/ft of vertical bore) $2 $3 $4 $5 $6 $7 $8 $9 $10 Open Loop Installation Cost ($100/ton) Contours represent fraction of geothermal capacity to the peak hourly heating load Full article available at

13 GHPs Applied to a Dairy Farm LOAD 1 LOAD 2 LOAD 3 HEATING & COOLING WATER COIL WATER-TO-WATER HEAT PUMP CIRCULATING PUMP SPACE HEATING & COOLING HOT WATER GENERATION (for dairy process) MILK CHILLING STORAGE TANK PROCESS DESCRIPTION THE GEOTHERMAL LOOP ACTS AS A HEAT SOURCE AND SINK FOR WATER-SOURCE HEAT PUMPS. IN ADDITION, THE GEOTHERMAL LOOP WILL ACT AS A THERMAL STORAGE MEDIUM, ALLOWING LOADS 2 AND 3 TO COMPLEMENT EACH OTHER ON BOTH SHORT AND LONG TIME SCALES. FOR EXAMPLE, LOAD 2 (HOT WATER GENERATION) WILL ONLY EXTRACT HEAT FROM THE LOOP WHILE LOAD 3 WILL ONLY REJECT HEAT TO THE LOOP. WHEN THESE TWO LOADS ARE IN DEMAND SIMULTANEOUSLY, THE NET LOAD ON THE EARTH LOOP APPROACHES ZERO. AT OTHER TIMES, THERMAL ENERGY WILL BE TRANSFERRED TO/FROM THE EARTH BY ONE LOAD AT CERTAIN TIMES, AND THEN RECOVERED BY THE OTHER LOAD AT LATER TIMES. 250 ft typical GEOTHERMAL LOOP CLOSED-LOOP EARTH HEAT EXCHANGERS IN VERTICAL BOREHOLE ARRAY (single U-tube type, high-density polyethylene)

14 Example Installations: Alternative Farming Center, TN Aquaculture operation in greenhouse structure (60 x 150 ) 90,000 gal. of water conditioned by five 5-ton water-water heat pumps for Tilapia production Approx. 100,000 lbs. fish/yr Air is conditioned by 4 water-air heat pumps (17 tons) Closed-loop vertical boreholes: 15 boreholes, 300 ft deep Annual operating cost savings exceed $30,000

15 CO emissions: > 285 tons Credit: P. Lambert, BMA Geo-Energy Inc., Montreal, Que. Example Installations: Greenhouse, Quebec 4+ acres, specializing in cut flowers Energy efficient construction; 7.2 million Btu/hr peak load Geothermal capacity: 58% (handles 89% of annual load) 640 boreholes, 105 ft $4/ft Installation cost: $1.2 million Incentives: $775,000 Annual operating cost savings: $115,000

16 Concluding Summary Geothermal heat pumps are an energy-efficient efficient technology Large agricultural applications are few, but potential is large More cost effective in some situations than others Simultaneous heating and cooling loads Low closed-loop cost High conventional fuel costs Reduced greenhouse gas emissions