Section IV : Some Technical Specifications of Geothermal Systems

Transcription

1 March 2010 Mumbai Delhi Chennai Kolkata Section IV : Some Technical Specifications of Geothermal Systems Introductory Seminar on Ground Source Heat Pump Systems SAP Programme T002 Funding support from Government of Canada gratefully acknowledged

2 2 Section Contents Conductivity Testing Physical Characteristics - Equipment Some Notes on Sizing Theory Thermal Storage A Quick Case Study

3 3 Conductivity Testing At a typical cost of ~ $ (i.e. between $5,000 and $ 10,000), is a TC test justifiable? For average residential systems, the answer is almost always NO, as testing usually costs as much as the entire drill job. For commercial or institutional projects the response is usually an equally loud YES.

4 4 Physical characteristics equipment Available Heat Pumps Horizontal ½ >< 10 Tons of Refrigerant (T.R.) Vertical ¾ >< 25 T.R. Console ½ >< 1 ½ T.R. Compact Vertical ¾ >< 3 T.R.

5 5 Physical characteristics equipment Type of Heat Pump Roof Units ½ >< 10 T.R. Fresh-air / outside units 3 >< 100 T.R.

6 6 Heating / Cooling Capacity, and power consumption Q: What s the optimal size for a cooling system?

7 7 Sizing theory loop sizing Sufficient length? An insufficient L can result in systemic problems (i.e. EWT can become lower than the permitted / usable rated level for the heat pump). In these cases, pump energy consumption rises as efficiency drops. An excessive L can result in unnecessary drilling / capital costs.

8 Sizing theory loop fluid selection Antifreeze Type Selection Heat transfer fluid is composed of water, a legally approved antifreeze (if required) and appropriate corrosion inhibitors, in conformity with best practises and referenced standards. 8 Antifreeze protection is necessary where loop temperatures risk dropping below 41 F (5 C), i.e H.P. and like states. Corrosion inhibitors are usually added to solutions in order to reduce oxidation of heat pump materials. One could also add stabilizers, to reduce the formation of the acids which help cause corrosion, or biocides for ferrous bacterial issues.

9 Sizing theory loop fluid selection Type of Antifreeze CGC Guidelines (2004)* Sélection of Antifreeze The three most commonly used antifreeze types in geothermal heat exchangers are: methanol; ethanol; propylene-glycol. Methanol is toxic and flammable. For ecological reasons, it s forbidden in certain regions in Canada. Methanol has pumping power and heat transfer properties which are superior to other options. 9 * Geoexchange Energy Systems Professional Design Guidelines, funded by CGC, June 2004,.

10 Sizing theory loop fluid selection Type of Antifreeze CGC Guidelines (2004)* 10 Ethanol is much less toxic to humans than methanol, although its environmental toxicity varies as a function of receptors and vectors (i.e. paths to spread).pumping characteristics and heat transfer properties of ethanol are noticeably inferior too those of methanol. Propylene glycol is a food-grade glycol, often used as a food additive. Its toxicity to humans and the environment is low; its flammability is low. Propylene glycol s viscosity (which influences pumping power requirements) is close to ethanol. Thermal exchange properties of propylene glycol are slightly inferior ot those of methanol and ethanol. * Geoexchange Energy Systems Professional Design Guidelines, funded by CGC, june 2004,.

11 Sizing theory loop fluid selection Type of Antifreeze ASHRAE study results 11 Many variables need to be taken in to account when it comes time to choose an antifreeze: Lifecycle costs (initial antifreeze cost and pumping power increment); Leaks / losses; Health risks; Fire risks; Environmental risk; Future-use risk (regulatory or availability). Study results indicate that propylene glycol is the ideal choice for geothermal systems in heating mode.

12 12 Sizing theory grouting Thermal grout Thermal conductivity of grout may be raised through the incorporation of fine sand such as chalk, plaster cement, quartz or silica. Does conductivity rise continously and linearly as sands are added? Thermally-enhanced grouts based on bentonite are on the market. Thermal conductivity oscillates between 0.45 and 1.45 Btu/foot-hour- F (or 0.78 and 2.51 W/m- C).

13 13 Sizing theory Design software All vertical loop length must conform to manufacturer specification, and be determined using an accepted software, and in the case of commercial buildings, have the approval of a registered engineer (per CGC and provincial law).

14 14 Thermal Storage Energy storage technology consists of placing a quantity of heat in a dedicated media, for ulterior use at a later time. There are several types of thermal storage such as: short term (diurnal cycle within 24 hours) Phase-change media thermal storage (latent heat, e.g. ice); Reservoir-based thermal storage (sensible heat); Latent storage requires less volume than sensible-heat storage, given that latent heat generally has much higher calorific / heat capacity. medium term (seasonal cycle within four seasons) thermal storage in aquifers, ground itself through boreholes, or in dedicated insulated earthen containers.

15 15 Thermal Storage Thermal aquifer storage is regulated in Canada according to Standard C Design and Installation of Underground Thermal Storage for Commercial and Institutional Buildings. Research is currently being conducted around the question of acceptable aquifer storage in Canada. For more information on this topic, see the industry magazine GeoConneXion from September CGC has also prepared a chapter on thermal storage as part of its new manual for Design and Installation of GeoExcange Systems.

16 16 A Quick Case Study Hôtel ALT Quartier Dix30 Project executed in Montreal by GENECOR and POLY-ÉNERGIE INC.

17 17 Case Study Hôtel ALT Quartier Dix30 Building Specs Surface of ft² with 159 rooms; high fenestration rate but with low-e glass, to maxmise natural light; heat pump in each room for maximum occupant comfort. Special Mention Winner of the CGC 2008 Prize for Project Excellence The most «green» building within a commercial center. Project executed in Montreal by GENECOR and POLY-ÉNERGIE INC.

18 18 Case Study Hôtel ALT Quartier Dix30 Wellhead connections

19 19 Case Study Hôtel ALT Quartier Dix30 PROJECT SAVINGS - Overall Total Initial Energy Expense: : * $232,999 * $13,856,500 MJ Total Final Energy Expense: $120,996 6,773,930 MJ Reduction of Energy Consumption: $112,003 7,082,570 MJ 48% 51% * Based on the average energy consumption of other Groupe Germain establishments with the same equipment characteristics (on-site laundry) and a similar number of rooms. PROJECT ENERGY SAVINGS BREAKDOWN Size of project: 7,340 m 2 Initial Final % Electricity savings: * 1,887,000 kwh/yr 1,215,720 kwh/yr 35.6 % Natural gas savings: * 186,446 m 3 /yr 63,271 m 3 /yr 66.1 %

20 20 Case Study Hôtel ALT Quartier Dix30 Energy Performance (unverified): Peak power calls lower than 225KW; when using desuperheater to preheat domestic waters in cooling mode system claims to reach a COP of 5.9; 90 % sized means that only peak heating needs are met with electricity: all other needs come from ground energy.

21 21 Case Study Hôtel ALT Quartier Dix30 Economic Impacts: unusually fast payoff of 1.8 years (with subsidies); owner has created a strategic advantage within regional hotel market. Environmental Impact: Reduction of m³ in natural gas consumption, leading to an estimated savings of 526 tons of GHG. Social Impact : 50% energy demand reduction, equivalent to removing 75 detached singlefamily homes from the energy system.

22 22 Case Study Hôtel ALT Quartier Dix30 Expected Reliability: an equipment lifetime greatly superior to that of a conventional HVAC system 50 years versus years. Expected productivity increase: No exterior equipment: easier to maintain - lower weather hazard reduced vandalism / external damage hazard; usually reduced or more flexible equipment configuration allows for space savings or increased space productivity