EQuilibrium TM Housing InSight Riverdale NetZero Active Solar Thermal System Riverdale NetZero is a new semi-detached duplex on a prime inner-city site in Edmonton, Alberta. Each two-storey home is approximately 234 m2 (2,519 sq. ft.), including the basement. As a winning project in the CMHC EQuilibriumTM Sustainable Housing Demonstration Initiative, the builder–developer, Habitat Studio & Workshop Ltd., has designed and constructed these homes with the intent that they are healthy and comfortable to live in, reduce energy use to a minimum, produce as much energy as they require in a year, conserve resources, have low environmental impact, and are marketable. One of the novel features of the Riverdale NetZero EQuilibriumTM project, which is highlighted in this EQuilibriumTM Housing InSight, is its solar combi-system where active solar thermal collectors are used for both domestic hot water and space heating. Technical Specifications The Riverdale NetZero solar combi-system utilizes liquid- based active solar thermal collectors that the Riverdale team estimates will provide 83% of domestic water heating and 21% of the annual space heating needs. Figure 3 shows the major components used in the heating, domestic hot water, and ventilation systems. The four main components of the solar combi-system include: n seven, vertically mounted, drainback solar collectors covering 21 m2 in area (Figure 1); n a 17,000 litre seasonal heat storage water tank; n a 300 litre domestic hot water (DHW) storage tank; and n a 7 kW (2 ton) water-to-water heat pump. Figure 1 South elevation showing the vertical solar thermal collectors To extract and store solar thermal energy, heated water from the solar collectors first passes through a heat exchanger To boost the amount of solar heat that can be drawn from in the 300 L DHW tank, and then through a second heat the seasonal storage tank, a 7 kW (2 ton) heat pump was exchanger in the 17,000 L seasonal heat storage water tank. added to the system. The heat pump is able to access an In addition to the solar thermal energy, two back-up heat additional 2 GJ (500 kWh) of heat in the seasonal storage sources were added to the design. The first is the electric tank by drawing the water temperature down from 30°C to heating element in the DHW tank. If the water in the 5°C. The resulting lower tank temperature also allows for seasonal storage tank is not sufficiently hot for space more solar thermal energy to be captured by the system due heating, hot water will be circulated from the DHW tank to the larger temperature difference between the tank and to the fan coil unit. the solar collector. Riverdale NetZero Active Solar Thermal System DHW is drawn from the 300 L DHW tank, which is maintained at a minimum temperature of 55°C by an electric heating element in the tank. The water that replenishes the DHW tank is drawn from the municipal water mains, and then is preheated by first going through a drain water heat recovery unit and then through a heat exchanger in the seasonal storage tank before entering the bottom of the DHW tank. The space heating system is a forced air system with heat supplied through a hot water coil in the fan coil unit. The heated water used in the fan coil unit can be drawn from a number of sources depending on the availability of water of sufficient temperature: 1. from the seasonal heat storage tank to the fan coil; 2. from the seasonal heat storage tank through the heat pump to the fan coil; or 3. from the DHW tank to the fan coil. Flat plate solar collectors were selected for this system, which have the following specifications: Figure 2 Utility Room Solar Plumbing Layout n Collectors are 1.776 m tall, 1.751 m wide, and 0.105 m deep; Implementation Considerations n A solar aperture area of 2.75 m ;2 The schematic in Figure 3 of the solar combi-system shows n A weight of 55 kg; and the complexity of the system, which in turn brought n A minimum life expectancy of 25 to 30 years. challenges into various aspects of the project. Although the system was designed to maximize the amount of The collectors were designed to be used as part of a energy drawn from the solar and heat recovery systems, drainback system. A drainback system utilizes gravity the Riverdale NetZero team concluded that the system was to drain the fluid from the collectors to a 30-litre storage somewhat difficult to design and install, complicated to tank whenever the water in the collectors is cooler than model and estimate performance, and complex to document the seasonal heat storage tank. This allows water to be and explain. used as the collector fluid without the risk of freezing, even in winter. The drainback tank needs to be installed Figure 2 shows the solar plumbing layout in the utility lower than the collectors in order to operate. room. Though the plumbing looks complex to describe, it can be simplified by explaining it as sections of heat-flow The 17,000 litre seasonal storage water tank was built loops that provide various heating functions: solar heat on site out of poured in place concrete. The tops and walls collection, domestic water heating, heat transfer between of the tank have RSI-8.8 (R-50) insulation, and the bottom tanks, flexible operating configurations, and ground loop has RSI-3.5 (R-20) insulation. cooling. Once commissioned, the piping will be insulated, and the pipes will be colour coded with directional arrows. 2 Canada Mortgage and Housing Corporation Riverdale NetZero Active Solar Thermal System When mounting solar devices for DW heating, it is often n Plumbing codes that do not address such systems recommended to install the collectors at an angle close to and the lack of familiarity of inspectors with solar the latitude of the site. While, the latitude in Edmonton is combi-systems. 53°N, the team opted for a vertical (90°) installation for the solar thermal collectors to maximise the winter solar heat Cost Implications production. Benefits of the vertical installation for solar The Riverdale NetZero team reported that the cost of thermal space heating systems include: the solar thermal system was approximately $37,000. They estimated that the system will supply approximately n Good winter solar gains; 4,150 kWh per year of solar energy to the house per year. n Elimination of snow accumulation on the panels which When the costs are spread over 25 years, the cost of solar can reduce the amount of solar energy absorbed; energy supplied by the system is $0.35/kWh. However, by n Maximisation of the capture of reflected solar energy discounting the $410/year fixed natural gas connection fee from snow covered ground; that is saved by using only solar energy and electricity to n Minimisation of overheating in the summer; and heat the home and domestic hot water, the 25-year price n More roof space for the photovoltaic (PV) system. of the active solar heat drops to $0.25/kWh. Given the weight and size of the collectors, a crane was used To the surprise of the team, without including the elimination to install the collectors. of the gas connection fee, the cost of energy produced from Another challenge in implementing the system was that the the solar thermal system was found to be greater than the interior space required for the tanks, pumps, and piping was 25-year price of electricity generated from the PV system. considerable as was the amount of wall space required for The 5.6 kW PV system, which generates approximately the system plumbing. 6,600 kWh of electricity per year, was reported to cost $54,000. Over 25 years, this represents a solar energy cost Installation problems encountered by the team when of $0.33/kWh. Note that neither of the energy price estimates commissioning the system included: includes maintenance or financing costs. n Air locks in piping and cavitation in the pumps; At first glance, it might not be evident why the solar n Leaks in valves, piping joints, pumps; and electrical energy would be less expensive than the solar n High level of complexity in developing settings and thermal energy: PV modules cost between $500 to algorithms for the control system to maximise $1,100 per square metre with efficiencies ranging from performance. 13% to 17%, while flat-plate solar thermal collectors cost Other challenges faced by the team in implementing their $300 to $400 per square meter with efficiencies ranging solar combi-system included: from 30% to 60%. n A lack of design tools for solar thermal systems for both For solar thermal systems with one or two collectors domestic hot water and space heating; supplying a solar DHW system, the energy price for n A lack of trades with basic training on solar thermal solar thermal heat would be much less than solar PV installation; and energy. However, beyond 1 or 2 collectors, the systems provide diminishing returns due to extended periods when the system is oversized and thus the solar resource is underutilized. The first collector meets most of the domestic hot water needs in the summer, whereas the energy provided from additional collectors is generally only utilized in winter and in the shoulder seasons. Thus every additional Canada Mortgage and Housing Corporation 3 Riverdale NetZero Active Solar Thermal System collector provides a smaller amount of usable energy for Summary roughly the same cost per collector. In comparison, none Harnessing solar energy is a key element utilized by all of these challenges are a factor for grid-connected solar PV EQuilibrium teams to approach and achieve net-zero annual systems, whose efficiencies are not dependent on the home’s energy consumption. Active solar systems can supply heat electricity demand. for both space heating and domestic hot water, as well as Technology Benefits electricity. The Riverdale NetZero team found that given the mismatch between when peak space heating demands Energy Savings occur compared to peak solar availability, a number of design strategies need to be applied in order to maximise the The Riverdale NetZero team estimates that the solar thermal fraction of space heating demands that can be met with solar system is expected to produce: energy. Some of these strategies can add complexity and n 1910 kWh/year of usable energy for DHW heating; and cost to the system that make implementing the solar space n 2240 kWh/year of usable energy for space heating. heating system more challenging then solar electric systems The sun’s renewable energy will thus provide 83% of the that do not face the same challenges. domestic water heating and 21% of the space heating needs. 4 Canada Mortgage and Housing Corporation Riverdale NetZero Active Solar Thermal System Figure 3 Schematic of Major Components of Riverdale NetZero Liquid-Based Active Solar Thermal System Canada Mortgage and Housing Corporation 5 Project Team Primary contact: Gordon Howell Howell-Mayhew Engineering firstname.lastname@example.org Builder–developer: Habitat Studio & Workshop Ltd. Builder contact: Peter Amerongen email@example.com For more information about this project and other EQuilibriumTM housing projects, visit CMHC’s website at www.cmhc.ca EQuilibriumTM What is EQuilibriumTM Housing? The national EQuilibriumTM Sustainable Housing Demonstration Initiative, led by Canada Mortgage and Housing Corporation (CMHC) brings the private and public sectors together to develop homes that address occupant health and comfort, energy efficiency, renewable energy production, resource conservation, reduced environmental impact and affordability. CMHC’s EQuilibriumTM housing initiative offers builders and developers across the country a powerful new approach to establish a reputation for building affordable, premium quality healthy homes that will meet the needs of Canadians now and well into the future. EQuilibriumTM housing combines a wide range of technologies, strategies, products and techniques designed to reduce a home’s environmental impact to an absolute minimum. At the same time, EQuilibriumTM housing also features commercially available, on-site renewable energy systems to provide clean energy to help reduce annual energy consumption and costs. EQuilibriumTM Housing InSight EQuilibriumTM Housing InSight present specific housing design strategies and technologies implemented in EQuilibriumTM housing demonstration projects. CMHC CMHC has been Canada’s national housing agency for more than 60 years. CMHC is committed to helping Canadians access a wide choice of quality, affordable homes and making vibrant and sustainable communities and cities a reality across the country. To find out more about how the Government of Canada and CMHC are working to build stronger homes and communities for all Canadians, call CMHC at 1-800-668-2642 or visit www.cmhc.ca ©2009, Canada Mortgage and Housing Corporation Printed in Canada Produced by CMHC 12-08-10 This publication is intended to highlight housing technologies and practices the builder teams utilized to construct their projects under CMHC’s EQuilibriumTM Sustainable Housing Demonstration Initiative. It is provided for general information purposes only and does not constitute an assessment, recommendation or an endorsement of any system, strategy, technique, technology, or product;. The predictions for building performance contained in the publication have been provided by the individual builder teams based on computer modeling and current understandings of best construction practices. Actual building performance may vary. Reliance on the information in this publication for the purpose of planning, design or construction activities would not be appropriate. If readers intend to engage in activities of that nature, they are advised to consult appropriate professional resources to determine what is safe and suitable in their particular case. Any reliance or action taken contrary to this advice is the full responsibility of the user. Canada Mortgage and Housing Corporation assumes no responsibility for any consequence, expense, claim, damage or loss arising from the 66741 use of the information contained in this publication.
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