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Adapting and assessing energy conversion technologies for integration in houses Swinton, M. C.; Entchev, E.; Bell, M.; Gusdorf, J.; Szadkowski, F.; Kalbfleisch, W.; Marchand, R. G.

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Adapting and assessing energy conversion technologies for integration in houses

Swinton, M.C.; Entchev, E.; Bell, M.; Gusdorf, J.; Szadkowski, F.; Kalbfleisch, W.; Marchand, R.

NRCC-47058

A version of this document is published in / Une version de ce document se trouve dans : Proceedings of the Joint NSC-NRC Workshop on Construction Technologies, Taipei, Taiwan, April 26-27, 2004, pp. 187-194

http://irc.nrc-cnrc.gc.ca/ircpubs

ADAPTING AND ASSESSING ENERGY CONVERSION TECHNOLOGIES FOR INTEGRATION IN HOUSES Michael C. SWINTON1, Evgueniy ENTCHEV2, Mike BELL2, John GUSDORF2, Frank SZADKOWSKI2, Walter KALBFLEISCH3, Roger MARCHAND4

ABSTRACT Twin research houses at the Canadian Centre for Housing Technology (CCHT) offer an intensively monitored real-world environment with simulated occupancy to assess the performance of small-scale energy conversion technologies. This paper presents one of several energy conversion technologies assessed at the twin house facility since 1998. Highlighted is the adaptation of a Stirling engine deployed in combined electrical and thermal integration of a house. Issues such as electrical grid connection, heat storage, control strategies and overall energy utilization are discussed. Small combined heat and power (CHP) plants that can generate electricity and heat at the single building are beginning to emerge as a viable alternative to large power generating stations in some circumstances. The next generation of CHP to be investigated will be fuel cells. While still in the developmental stage, fuel cells are promising for small-scale CHP applications, and several Canadian companies are currently involved in the development of these systems. Once the technology is developed, the next challenge will be the integration into the building’s electrical and heating (HVAC) systems. Issues such as CHP system sizing, need for storage, meeting peak loads, dissipation of excess heat, etc. will need to be addressed. Field testing first generation prototypes in a well controlled but realistic residential setting would significantly accelerate development of these systems. Keywords: energy conversion technologies, space heating, water heating, electrical generation, combined heat and power generation. INTRODUCTION In 1998, the Canadian Centre for Housing Technology was commissioned and built by a partnership involving National Research Council Canada, Natural Resources Canada, and Canada Mortgage and Housing Corporation. The twin energy efficient research houses, built by a local builder on the NRC campus in Ottawa in the fall of that year, were commissioned and benchmarked through 1999. The houses are extensively monitored for energy performance and thermal comfort. The two houses have different roles and are labeled accordingly: the reference house and the test house. Reference house The reference house is typical 2-storey wood-frame house, with 210m2 livable area. It is built with a cast-in-place concrete basement, and with style and finish representative of current houses available on the local housing market in Ottawa. It meets the R-2000 Standard (Canada’s voluntary standard for energy efficient housing) while featuring a standard Canadian wood-frame construction . It has a high efficiency sealed combustion condensing gas furnace, a power vented conventional hot water heater and a heat recovery ventilator, along with a number of well insulated and tight assemblies to complete the R-2000 package.

1

2 3 4

Senior Research Officer, Building Envelope and Structure Program, Institute for Research in Construction, National Research Council Canada, e-mail: [email protected] Researcher, Natural Resources Canada Manager, Facilities Engineering Administrative Services and Property Management, National Research Council Canada Technical Officer, Indoor Environment Program, Institute for Research in Construction, National Research Council Canada

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Photo 1. Reference House (near) and Test House (far) at the Canadian Centre for Housing Technology. Test house The test house is initially identical to the reference house and is benchmarked every season to ensure that it is as close to identical as practical. The test house is then modified to assess the impact of innovative energy systems and components on the overall energy and comfort performance of the house. The test house is used to assess only one component at a time, on a day-by-day basis – each day is an experiment, with results presented for each season (heating or cooling) to develop characteristics of performance for the technology. On completion of the assessments, the test house was returned to its starting (benchmark) configuration and the benchmark was re-confirmed. Selected characteristics of the CCHT research houses are reported in Table 1. Table 1. Selected Characteristics of the CCHT Research Houses Component Construction Standard Storeys Livable Area Basement Garage Attic Walls Rim Joists Exposed floor over the garage Basement Walls Basement floor Windows Window Area Air Barrier System Airtightness Heat recovery Ventilator Furnace Hot Water Heater Air conditioning

Characteristic R-2000 2 210 m2 Poured concrete, full basement. Two-car, recessed into the floor plan; isolated control room in the garage RSI 8.6 RSI 3.5 RSI 3.5 RSI 4.4 with heated/cooled plenum air space between insulation and sub-floor. RSI 3.5 in a framed wall. No vapour barrier. Concrete slab, no insulation Low-e, insulated spacer, argon filled, with argon concentration measured to 95%. South Facing: 16.2 m2 Total: 35.0 m2 Exterior, taped fibreboard sheathing with laminated weather resistant barrier. Taped penetrations, including windows. Reference 1.07 ach @ 50 Pa; Test House 0.97 ach @ 50 Pa High Efficiency (84% nominal) Condensing gas @ 91% efficiency (as measured) Conventional, induced draft @ 67% efficiency (as measured). High efficiency - SEER 12 (nominal)

Simulated Occupancy Controls The houses are equipped with a sophisticated control system based on home-automation technologies, which operate lighting, plumbing and major appliances (stove, washer, dryer, and dishwasher). Generating the equivalent amount of heat with lamps simulates heat release associated with occupant presence and the operation 188

of small appliances. houses.

This system of simulated occupancy was designed to be identical and synchronized in both

The twin houses have been used to assess a number of energy technologies using a methodology developed for side-by-side testing [1-8], including: combination heating systems that supply both space heating and hot water, thermostat setback controls, electronically commutated motor for the air circulation fan in the forced-air furnace, interior and exterior shading for cooling load control, a grey water heat recovery device for showers, and a combined heat and power (CHP) system[9], using a small gas fired Stirling engine to provide hot water for domestic use, space heating, and some of the house’s electricity needs.

Photo 3. The Stirling Engine Adapted for CHP in the Test House

Photo 2. Two Combination Water Heaters next to the conventional water heater on the right.

COMBINED HEAT AND POWER GENERATION – A CASE STUDY Small combined heat and power systems which can generate thermal and electrical energy at a community or even single household level are beginning to emerge as a viable alternative to large and expensive power generating stations in some circumstances. In a combined heat and power application, electricity is produced where it is needed (distributed generation (DG)) and opportunities exist for heat recovery from waste heat, which boosts efficiency. As well, emissions can be reduced by using fuel sources more efficiently and possibly by using cleaner fuels. Events like the 1998 Ice Storm in Eastern Canada, rolling brownouts in California, and the recent blackout in Eastern North America (August 2003) have increased homeowners’ interest in small power plants that can provide primary or back-up power for their houses. There are several technologies being developed for residential CHP. At this time, promising clean-fuel CHP technologies include Stirling engines and fuel cells. Residential Stirling engine CHP systems appear to be closest to commercialisation. However, fuel cell technologies, while still in the developmental stages, offers much promise for combined heat and power. Units ranging in size from 1 to 10 kW could provide all or part of the electricity and heat required by a typical Canadian household. Some systems are intended for remote, off-grid applications, while others are designed for houses that are grid-connected. In either case, heat co-generated with electricity generation can be recovered to provide space and water heating to the house, as well as other potential uses. Several Canadian companies are currently focussing on the development of residential fuel cell CHP systems. OBJECTIVES OF THE CHP PROJECT One objective of the CHP project was to develop and demonstrate a test facility at the CCHT with the capability to assess residential CHP systems and their integration into houses, under real-world conditions. The project was intended to result in a highly sophisticated “residential CHP-ready” facility operated by a multidisciplinary team of professionals experienced in installation, commissioning, monitoring, analysis, optimization and modeling of such systems. Another objective was to quantify the performance of one early residential CHP system (Stirling engine based, see photo 3) and to examine building integration issues such as HVAC interface, storage, control, CHP system 189

sizing, etc. This information should be useful to residential CHP manufacturers, utilities and others to evaluate building integration issues, to evaluate the CHP system under test in particular and to gain impressions of residential CHP in general. APPROACH The project consisted of designing and implementing the facility modifications in the following areas: • Electrical modifications to integrate the CHP system into the CCHT Test House’s electrical system, and to allow the CHP to export electricity to the grid. This work included the design of the electrical modifications, added wiring, safety switches, electrical panels, metering for the datalogging equipment and power quality meters. • Design and installation of the Balance of Plant (BOP) (see figure 1) to integrate the CHP system into the Test House’s space and water heating system. Added components of the BOP included a hot water storage tank, pumps and piping, and controls. These were integrated with an existing water heater and air handler that had been adapted to supply both space and water heating to the house in a previous project. • Installation and connection of the CHP system. • Specification and installation of several control systems for the CHP and BOP. • Development of an extensive monitoring package for each of the sub-systems that formed the CHP System. Once the modifications were completed, the test house and CHP were commissioned and experiments were performed from March to June 2003. Note that we did not use the reference house in the CHP assessment.

Figure 1. Schematic Diagram of The Balance of Plant and Sensors.

The experimental nature of this project afforded the opportunity to configure the same BOP components in two different ways to investigate whether the strategy for directing heated water and cooler return water had an impact on the operating efficiency of the CHP and the BOP, as well as that of the overall system. These approaches are described below. Setup 1: The storage tank ST is used as a supplementary heater to the HWT (warm water in storage circulated to HWT, and cooler HWT water back to storage. HWT gets the fresh water supply) Setup 2: ST is in series with the HWT (hot water from the hot water storage tank circulated to HWT and then to space heat load and back to ST, or to water heating, with fresh water into ST) In both configurations, the CHP unit is the heating source to the storage (ST), with a closed loop and heat exchangers linking the CHP unit to the storage. 190

Electrical Modifications The electrical modifications were designed by the Administrative Services and Property Management (ASPM) unit of NRC with input from the Working Group and the Steering Committee, as well as local regulatory authorities. ASPM is responsible for all buildings on the NRC campus, including electrical and HVAC systems. ASPM had previous experience integrating their own commercial-sized CHP system into the grid, and their expertise contributed to the project, including a good understanding and working relationship with local regulatory authorities. The modifications were made to accommodate the installation of combined heat and power (CHP) systems having a generating capacity up to 40 kWe, for either grid-dependent operation (this project) or stand-alone, grid-independent operation (possible future projects).

The following wiring changes were made to each test house: 1.

Three additional bi-directional, pulse generating kilowatt-hour meters, and an additional power quality meter were added for monitoring purposes. 2. A weatherproof, lockable disconnect switch was installed on the exterior of each house to meet requirements of rule 84-028 of the Canadian Electrical Code. 3. A four-pole transfer switch was installed to allow various generator configurations without re-wiring. 4. A 100-amp disconnect / isolating switch with 20-amp fuses was installed to protect and isolate the CHP generator under test. A schematic diagram of the integration of these elements to the Test house is shown in Figure 2.

Figure 2.

Schematic Diagram of the Upgraded Wiring and Metering in the CCHT Houses.

RESULTS Monitoring took place between March 13 and June 10 2003. For analysis purposes, the overall monitoring period was split up into 39 individual ‘runs’ for which energy balances and system efficiencies were calculated. In essence, each ‘run’ can be viewed as an individual experiment. Some of the characteristics of these runs include:

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The duration of each run ranged from 23 to 65 hours, with an average of 40 hours per run. The duration of runs varied due to CHP unit problems and changes from one Set-up to another. • 11 runs (497 hours) were in Setup #1. • 16 runs (594 hours) were in Setup #2. • 3 additional runs occurred during which the CHP unit failed, and were not analyzed with the others. In all runs, the house space heat and hot water demands were met. Eight runs used additional heat from the HWT gas burner. This was due to the control strategy and HWT setting, not to lack of available heat from the CHP. For these cases, the gas use by the HWT was 6% or less of total gas use. Analysis Approach - Calculation of Efficiencies from Energy Balances The analysis kept track of three efficiencies: the CHP unit efficiencies (both electrical and thermal), the BOP Efficiency (thermal) and the System Efficiency (a combined electrical and thermal efficiency). The efficiencies are, by definition, an account of energy outputs divided by energy inputs. Tables 2 and 3 present the monitoring results of the 39 runs for the CHP unit, the Balance of Plant (BOP), and the System as a whole.

Table 2. CHP Unit Efficiencies

Table 3. Balance of Plant and Total System Efficiencies

CHP Unit Efficiency The CHP unit efficiency increased only slightly with an increase in the thermal load. This is probably due to lower average inlet temperatures of the cooling system for the CHP, associated with higher space heating loads. Then there is no demand for space heat (hot water demand only), the average demand on the BOP is 0.48 kW. There were 10 runs with no space heating. With no space heating, demand on BOP varied from 0.39 to 0.62 kW, due to different start and end times (different HW demands), and different CHP unit run time patterns. All three curves in Figures 3,4 and 5 are projected to reach close to the CHP unit output capacity (6.5 kW. At 75% BOP efficiency, that’s 4.88 kW of delivered heat)

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The CHP unit heating efficiency varied from 74% for hot water only to about 79% at system capacity. The CHP unit electrical efficiency varied from 5.5% to about 9% at system capacity. The CHP unit total efficiency varied from 79.5% for HW only to about 88% at system capacity. BOP and System Efficiency The energy efficiencies of both the BOP and the System show significant dependence on thermal load. This is due to the fact that the stand-by losses from the BOP are relatively constant, while the useful heat varies mainly with space heat load. According to the regressions, the BOP efficiency varies from 47.6% for HW only to near 80% at CHP capacity, and the system efficiency varies from 41% for HW only to over 70% at CHP capacity. Results by Setup Configuration Finally, there were only small differences between the two setups investigated, although setup #2 appeared to generate a slightly better electrical efficiency. Analysis of each setup for dependence on BOP Output showed little appreciable difference in the sensitivity of the setup to that factor. Note that the last two columns of Table 4 divide the system energy efficiency (column 9) into electrical and heat efficiencies. Table 4. Summary of Efficiencies by Setup

Potential for Electrical Power Reduction and Export to the Grid Two examples were selected to highlight how much electricity is generated by the CHP in proportion to house electricity demand, and where that electricity goes. The summary electricity balance over each run shown in Table 5 illustrates the overall impact of the system. It can be seen that whereas most of the electricity produced by the CHP unit goes to the house (94 and 98% in these examples), there were still instances of export to the grid (6 and 2%), even with this small electrical generator that is regulated on a heat-demand basis. When the house electrical demand is analyzed, it can be seen from these two examples that the CHP does supply important percentages of the house’s electricity requirement (43 and 25% in these examples). Table 5.

Example Electricity Balance for the CHP Supply and the House Demand

CHP CHP electricity generation CHP electricity used by the house CHP electricity exported to the grid Demand Account Total house electricity consumption Electricity supplied by the grid Electricity supplied by the CHP

Run 13 (April 1 & 2) Total Electricity, kWh 9.95 9.36 0.60 21.74 12.38 9.36

100% 94% 6%

Run 23 (April 24) Total Electricity, kWh 5.34 5.23 0.11

100% 98% 2%

100% 57% 43%

20.72 15.49 5.23

100% 75% 25%

%

%

FUTURE RESEARCH OF OUR INTEREST The Stirling engine CHP was used to demonstrate the CHP testing and monitoring capability of the converted CCHT test house. While the testing of the CHP itself was not intended to be exhaustive, its performance during the demonstration suggests that the system has promise and merits follow-up work to address the above issues. Areas of interest for further research include: • The design and control of the Balance of Plant (for heat storage and distribution), and optimization to 193

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minimize shutdown of the CHP, and maximize the overall efficiency of that part of the system. Extend the work by analyzing the performance of the reference house with benchmark technologies as a reference to CHP. The role of a heat-driven CHP unit in the summer, when the thermal load is small and the BOP heat losses to the house are relatively high. The first fuel cell is being installed in the test house in the spring of 2004 as a CHP system connected to the electrical grid and the house space and water heating supply. This unit will offer different challenges for integration into this small building, because of its greater electrical and thermal output. Issues of available heat utilization may call for special equipment, such as a small absorption chiller unit to produce air conditioning from the waste heat. Use of available data could be made to benchmark models for CHP units. Summer electrical load management technologies could be investigated as well. CONCLUDING REMARKS

Experimental work on assessing the performance of energy conversion technologies is ongoing at the Canadian Centre for Housing Technology. A number of such energy technologies have already been assessed, including: combination heating systems that supply both space heating and hot water, thermostat setback controls, electronically commutated motor for the air circulation fan in the forced-air furnace, interior and exterior shading for cooling load control, a grey water heat recovery device for showers, and a combined heat and power (CHP) system, using a small gas fired Stirling engine to provide hot water for domestic use, space heating, and some of the house’s electricity needs. Collaboration opportunities exist in the area of using existing performance datasets to analyze, model and optimize the application of these technologies, and new experiments can be envisaged to assess emerging technologies such as small fuel cells. REFERENCES Brown, W.C., 1980. Mark XI Energy Research Project - Comparison of Standard and Upgraded Houses. Division of Building Research (now Institute for Research in Construction), National Research Council Canada. Building Research Note No. 160, June 1980. Lee, E.S. DiBartolomeo, D.L. and Selkowitz, S.E. 1998. Thermal and Daylighting Performance of an automated venetian blind and lighting system in a full scale private office. Energy and Buildings 29, 1998, 47-63. Quirouette, R.L., 1978. The Mark XI Energy Research Project – Design and Construction. Division of Building Research (now Institute for Research in Construction), National Research Council Canada. Building Research Note No. 131, October 1978. Rayment, R., Hart, J., and Whiteside, D. 1993. The DoE/BRE Energy and Environment Test Houses. Building Research Establishment Internal Report N196/92, January 1993. Rayment, R., Hart, J., and Whiteside, D. 1997. Comparison of moisture clearance by trickle and ducted systems in Swedish test houses. Building Research Establishment Internal Report N101/97, August 1997. Rayment, R. 1998. personal communication, Garston, United Kingdom, April 8, 1998. Swinton, M.C.; Moussa, H.; Marchand, R.G. "Commissioning twin houses for assessing the performance of energy conserving technologies," Performance of Exterior Envelopes of Whole Buildings VIII Integration of Building Envelopes (Clearwater, Florida, Dec, 2001), pp. 1-10, 2001 (NRCC-44995). Swinton, M.C.; Entchev, E.; Szadkowski, F.; Marchand, R.G. "Benchmarking twin houses and assessment of the energy performance of two gas combo heating systems," 9th Canadian Conference on Building Science and Technology (Vancouver, B.C. 2003-02-27), pp. 365-381, Feb, 2003 (NRCC-38459). Bell, M., Swinton, M.C., Entchev, E., Gusdorf, J., Kalbfleisch, W., Marchand, R.J., Szadkowski, F., Development of Micro Combined Heat and Power Technology Assessment Capability at the Canadian Centre for Housing Technology. Contract report, Canadian Centre for Housing Technology, December 8, 2003.

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