RESEARCH REPORT. Solar Energy Potential for the Northern Sustainable Houses Projects

Transcription

1 RESEARCH REPORT Solar Energy Potential for the Northern Sustainable Houses Projects

2 CMHC HOME TO CANADIANS Canada Mortgage and Housing Corporation (CMHC) has been Canada s national housing agency for more than 65 years. Together with other housing stakeholders, we help ensure that the Canadian housing system remains one of the best in the world. We are committed to helping Canadians access a wide choice of quality, environmentally sustainable and affordable housing solutions that will continue to create vibrant and healthy communities and cities across the country. For more information, visit our website at or follow us on Twitter, YouTube and Flickr. You can also reach us by phone at or by fax at Outside Canada call or fax to Canada Mortgage and Housing Corporation supports the Government of Canada policy on access to information for people with disabilities. If you wish to obtain this publication in alternative formats, call

3 SOLAR ENERGY POTENTIAL FOR THE NORTHERN SUSTAINABLE HOUSES PROJECTS Arctic Energy Alliance August 2014

4 DISCLAIMER This Project was funded by Canada Mortgage and Housing Corporation (CMHC) and the Program for Energy Research and Development (PERD) of Natural Resources Canada, but the views expressed are the views of the author(s) and do not necessarily reflect the views of CMHC nor NRCan. CMHC s and NRCan s financial contribution to this report does not constitute an endorsement of its contents. 1

5 EXECUTIVE SUMMARY The Solar Energy Assessment for the Northern Sustainable Houses (NSH) Project explores the solar energy potential of northern housing. Although the annual solar potential in Canada s North is comparable to the solar potential in its southern urban centers, insights are needed on how the design of northern housing might be adapted to better capture solar energy while addressing the unique challenges of designing, building and operating housing in the North. The study focuses on the four Northern Sustainable Houses (NSHs) that were designed and built in the three territories to explore innovative models of culturally-appropriate, energy efficient, housing in the North. The NSHs are presented as illustrative case studies for optimizing the design and orientation of the roofs (upon which solar panels could be mounted) with respect to annual solar radiation exposure. Additionally, recent research findings on the performance of the solar energy systems installed on two of the NSH projects are presented. The findings of the project characterize the sensitivity of the annual solar energy potential of houses to their orientation and the tilt angle of the roofs that receive solar energy. Although the houses are located in different cities across the North, the findings were relatively consistent. For instance, while it is advantageous from a solar gain point of view to have the longest axis of a house oriented east-west (i.e.; 90 0 to south to provide the most opportunity for one of the roof surfaces to face south), being off by 15% does not represent a significant impact on solar potential. However, being off by 90 0 could reduce tha annual solar radiation falling on the roof surface by 30% or more. Given the high latitudes of the NSH locations, raising the roof angle and thereby increasing the amount of roof area to receive solar energy tended to increase the annual solar energy potential. With respect to roof tilt angle, it was found that moving from a relatively low slope (e.g.; 4:12) to higher slopes tends to increase the annual solar energy potential of south-facing roof surfaces. However, as the slope approaches 90 0, the annual solar potential begins to decline due to the higher angle of the sun to the vertical surface during the summer when solar energy potential peaks. The study also looked at project-specific modifications to the roof structure of several of the projects to provide additional roof area. Though not part of the modeling study, data from the performance monitoring of the solar PV and solar thermal systems installed in two of the NSH projects is provided for context. The monitoring data demonstrates the strong adverse impact of the winter months on solar potential when little or no direct sunlight is available in many locations in the North. The impact of the long hours of available sunlight during the summer months is also readily apparent. The comparison of modeling estimates to actual production found the models over-estimated solar energy production though it is not clear whether or not this reflected limitations of the models used, the modeling assumptions or operational problems with the solar energy systems. Based on the information used to inform and guide the research, general guidance on the solar design of housing in the North was developed. 2

6 RÉSUMÉ L initiative d évaluation de l énergie solaire pour les maisons durables construites pour le Nord avait pour objet d évaluer le potentiel en énergie solaire des habitations des régions nordiques. Bien que le potentiel solaire annuel dans le Nord canadien soit comparable à celui des centres urbains plus au sud, il faut trouver des pistes de solution sur la manière d adapter le logement du Nord pour mieux capter l énergie solaire tout en composant avec les difficultés particulières liées à la conception, à la construction et à l exploitation de logements dans le Nord. L étude dont il est question ici met l accent sur les quatre maisons durables pour le Nord qui ont été conçues et construites dans trois territoires afin de faire l essai de modèles innovants de maisons pour le Nord, appropriées sur le plan culturel et éconergétiques. Les maisons durables construites pour le Nord servent d études de cas pour illustrer la façon d optimiser la conception et l orientation des toits (sur lesquels on pourrait ériger des panneaux solaires) par rapport à l exposition au rayonnement solaire annuel. De plus, on y présente des résultats de recherches inédits sur la performance des installations à énergie solaire de deux de ces maisons. Les résultats de l étude délimitent la variabilité du potentiel solaire annuel des maisons selon leur orientation et l angle d inclinaison des toits qui reçoivent l énergie solaire. Même si les maisons sont situées dans des villes différentes à travers le Nord, les résultats étaient relativement uniformes. Par exemple, bien qu il soit avantageux du point de vue des gains solaires d orienter la maison suivant l axe le plus long orienté d est en ouest (c'est-à-dire à angle droit avec le sud afin de maximiser les gains sur une surface de toit orientée au sud), un écart de 15 % n a pas une incidence importante sur le potentiel solaire. Toutefois, un écart de 90 pourrait réduire de 30 % ou plus le rayonnement solaire annuel qui atteint la surface du toit. Compte tenu des hautes latitudes des emplacements des maisons durables construites pour le Nord, un plus fort angle d inclinaison des toits contribuait généralement à accroître le potentiel solaire annuel. En ce qui a trait à l inclinaison du toit, on a découvert qu en passant d un toit à faible pente relative (c'est-à-dire 4 : 12) à des pentes plus inclinées, on obtenait généralement une augmentation du potentiel solaire annuel des surfaces orientées au sud. Cependant, à mesure que la pente approche les 90, le potentiel solaire annuel commence à diminuer parce que l angle de rayonnement est plus grand par rapport à la verticale durant l été, lorsque l énergie solaire potentielle atteint sa valeur de pointe. L étude s est également penchée sur des modifications particulières à la structure du toit de plusieurs maisons, lesquelles visaient à accroître la superficie du toit. Bien qu elles ne faisaient pas partie de l étude de modélisation, les données tirées du suivi de la performance des panneaux solaires thermiques et photovoltaïques installés dans deux des maisons durables construites pour le Nord ont été présentées pour donner davantage de contexte. Les données du suivi montrent l incidence négative des mois d hiver sur le potentiel solaire lorsque peu ou aucun rayonnement solaire n est disponible dans de nombreux endroits dans le Nord. L impact des longues heures d ensoleillement durant les mois d été est également très évident. Une comparaison des prévisions du modèle par rapport à la production réelle révèle que le modèle surestimait la production d énergie solaire, bien que l on ignore si la faute revient aux limitations des modèles utilisées, aux hypothèses de modélisation ou aux problèmes liés à l exploitation des installations à énergie solaire. En se fondant sur les informations utilisées pour étayer et diriger la recherche, on a élaboré un guide d orientation générale sur la conception solaire des maisons construites pour le Nord. 3

7 National Office 700 Montreal Road Ottawa ON K1A 0P7 Telephone: (613) Bureau national 700 chemin de Montréal Ottawa ON K1A 0P7 Téléphone : (613) Puisqu on prévoit une demande restreinte pour ce document de recherche, seul le résumé a été traduit. La SCHL fera traduire le document si la demande le justifie. Pour nous aider à déterminer si la demande justifie que ce rapport soit traduit en français, veuillez remplir la partie ci-dessous et la retourner à l adresse suivante : Centre canadien de documentation sur l habitation Société canadienne d hypothèques et de logement 700, chemin Montréal, bureau C1-200 Ottawa (Ontario) K1A 0P7 Titre du rapport: Je préférerais que ce rapport soit disponible en français. NOM ADRESSE rue App. ville province Code postal No de téléphone ( )

8 TABLE OF CONTENTS Executive Summary... 2 Résumé... 3 Table of Contents... 4 Figures... 5 Tables Introduction Canada s North Energy Challenges and Solar Opportunities Climate considerations for the NSH locations Location Solar Radiation Other Climate Effects Solar Potential for the NSH Houses Dawson E/2 NSH Dawson E/9 NSH Inuvik NSH Arviat NSH Site Planning and Community Design Conclusions Bibliography APPENDIX A Monitoring results of solar technology performance in NSHs Monitoring and modeled results of the Inuvik NSH solar PV production Monitoring and modeled results of the Inuvik NSH solar hot water production Monitoring and modeled results of the Dawson E/9 NSH solar hot water production APPENDIX B Design guidance for optimizing solar energy for housing in Canada s North Photovoltaic Electricity Solar Domestic Hot Water Passive Solar APPENDIX C Annual PV potential & solar radiation available for Northern communities Yukon Nunavut Northwest Territories

9 FIGURES Figure 1-1: Total electricity generation in all three territories by source Figure 2-1: Geographical location of the four NSHs Figure 2-2: Mean daily global annual solar radiation map of Canada Figure 2-3: Effect of changing orientation on monthly solar radiation Figure 2-4: Effect of changing tilt on monthly solar radiation Figure 2-5: Monthly available solar radiation of the NSH locations compared with Ottawa Figure 2-6: Monthly outdoor temperature of the NSH locations compared with Ottawa Figure 3-1: Floor plan of the Dawson E/2 NSH Figure 3-2: Dawson E/2 NSH south elevation Figure 3-3: Dawson E/2 NSH west and north elevation Figure 3-4: Orientation of Dawson E/2 NSH roof Figure 3-5: Pitch of Dawson E/2 NSH roof Figure 3-6: Floor plan of the Dawson E/9 NSH Figure 3-7: Dawson E/9 NSH south and west elevation Figure 3-10: Orientation of Dawson E/9 NSH roof Figure 3-11: Pitch of east-west facing roof Figure 3-12: Pitch of south facing porch Figure 3-8: Dawson E/9 NSH west elevation Figure 3-9: Dawson E/9 NSH east elevation Figure 3-13: Two-panel solar hot water system on Dawson E/9 NSH porch roof Figure 3-14: Solar hot water storage tank Figure 3-15: Floor plan of the Inuvik NSH Figure 3-16: Inuvik NSH southeast elevation Figure 3-17: Inuvik NSH southeast and northeast elevations Figure 3-18: Inuvik NSH northeast elevation Figure 3-19: Orientation of the Inuvik NSH roof Figure 3-20: Pitch of southeast and northwest facing roofs Figure 3-21: Solar hot water panels on roof of Inuvik NSH Figure 3-22: Large hot water storage tank for solar heated water for Inuvik NSH Figure 3-23: PV on the roof of Inuvik NSH Figure 3-24: Inverters for the PV on Inuvik NSH Figure 3-25: Floor plan of the Arviat NSH. Source: NHC Figure 3-26: Arviat NSH southeast elevation Figure 3-27: Arviat southeast and southwest elevations Figure 3-30: Overview of orientation of roof & façade Figure 3-28: Orientation of the Arviat NSH roof. Credit: Hamlet of Arviat Figure 3-29: Pitch of northwest facing roof. Credit: NHC Figure 4-1: Plateau Development Scheme for the City of Iqaluit Figure A-1: Comparison of monitoring results from different sources (Inuvik NSH) Figure A-2: Solar PV monitoring results vs. RETScreen model (Inuvik NSH) Figure A-3: Solar hot water monitoring (4 panels) vs. models (Inuvik NSH) Figure A-4: Solar hot water monitoring (2 panels) vs. models (Dawson E/9 NSH) Figure B.71: Sizing of solar hot water systems

10 TABLES Table 2-1: Climatic and building information for the four NSHs Table 2-2 Summary of available annual global solar radiation for the NSH locations & Ottawa Table 3-1 Available annual solar radiation for various orientations and tilt angles Table 3-2 Summary of different design scenarios for Dawson E/2 NSH solar integration Table 3-3: Available annual solar radiation for various orientations and tilt angles Table 3-4 Summary of different design scenarios for Dawson NSH E/9 solar integration Table 3-5: Available annual solar radiation for various orientations and tilt angles Table 3-6: Summary of different design scenarios for Inuvik NSH solar integration Table 3-7 Available annual solar radiation for various orientations and tilt angles Table 3-8 Summary of different design scenarios for Arviat NSH solar integration Table C-1: PV Potential of Yukon communities for varying tilts Table C-2: PV Potential of Nunavut communities for varying tilts Table C-3: PV Potential of Northwest Territories communities for varying tilts

11 1 INTRODUCTION Renewable energy technologies such as solar photovoltaic (PV) or solar thermal systems have the potential to offset the energy needs of housing in northern Canada. The annual total available solar radiation in the North is actually very similar to southern Canada s urban centers. Rising fuel prices and more competitive costs for solar technologies are driving interest in using on-site renewable energy generation to reduce fossil fuel dependency. Further, as fuel has to be imported to, and stored in, most northern locations, the environmental concerns associated with fuel spillage and pollutant emissions can be partly addressed by local solar energy generation. In response to the high heating loads and costly energy, northern housing design has become more energy efficient. However, at some point, there are diminishing returns associated with the application of energy efficiency measures and it becomes more practical, and affordable, to consider ways to harness greater amounts of renewable solar energy to meet household needs. However, questions remain regarding the optimal orientation and surfaces of houses to capture solar energy in the North. To explore the solar energy potential for northern housing, Canada Mortgage and Housing Corporation (CMHC) supported a modeling study of the four Northern Sustainable Houses (NSHs) that were constructed by northern housing providers to demonstrate culturally appropriate, energy efficient housing options. The study assessed how changes to the orientation and roof slope of the NSH projects impact solar energy gathering potential. It should be noted that while all the general observations and guidelines apply across the North, locationspecific considerations should be taken into account when planning and designing solar energy systems. 1.1 Canada s North Canada s northern territories account for over one-third of the land area and only 0.3 per cent of the Canadian population. Of the 115,000 northern residents, nearly half live in the three territorial capitals of Whitehorse, Yellowknife and Iqaluit, while the remaining population is spread out in over 88 communities, many of which are remote and difficult to access. The challenges of building, operating and maintaining housing in the North are many. They include extreme conditions due to the harsh climate, impacts of climate change, high energy and material costs, limited transportation infrastructure, short construction seasons, and long supply chains. Building materials and supplies must be shipped in as they are not generally manufactured locally. The cold climate limits the construction/transportation season and contributes to high home heating costs. Climate change is impacting the integrity of permafrost which is destabilizing buildings, roads and other infrastructure. In many northern communities, the shortage of skilled labour adds to the high cost of construction and maintenance. Transportation options differ throughout the North; some locations such as Inuvik and Dawson City are accessible by road, while in Arviat, supplies can only be sent in by ocean freighter which means higher costs and more complex logistics. Transportation to other locations includes seasonal ice roads, seasonal ferry crossings, and fly-in only communities. 7

12 1.2 Energy Challenges and Solar Opportunities Though rich in natural resources such as crude oil and natural gas, Canada s North relies heavily on imported fossil fuel from southern locations. The majority of residential heating in the North is provided by heating oil or propane that has to be shipped to and stored in each community. Natural gas has historically been available in some communities, but the supply going forward is uncertain. Given the cold climate, remote locations and high heating loads, the cost of energy for households in the North can be onerous. The electrical grids in all communities in Nunavut, the majority in the Northwest Territories and a few communities in the Yukon are not connected to any other community. The electricity generation is predominantly hydro in the Yukon, hydro and diesel (with some natural gas) in NWT and entirely diesel in Nunavut. The electricity price per kilowatt-hour (kwh) in some communities is over 10 times higher than the Canadian average. The per capita energy cost in the North is almost double the national average (National Energy Board, 2011). The local nature of electricity production and distribution means that power outages are more common across the North than in the South. Hydro Natural Gas Diesel Figure 1-1: Total electricity generation in all three territories by source. Note that charts are scaled to indicate relative total electricity generation by territory. Credit: Modified from (Governments of the Northwest Territories, Nunavut, and Yukon, 2011). With the objective of reducing energy consumption and offsetting fossil fuel use (both on-site and at the local electricity generating plant), the potential to design energy efficient houses and to integrate renewable energy systems is promising for the North. The relatively high energy costs often offer a more competitive payback time for well-proven solar technologies such as photovoltaic (PV) and solar hot water systems. The simple, off-the-shelf solar technologies that have little to no moving parts and minimal maintenance requirements can fit in well with the northern context where sophisticated systems can be under-maintained, difficult to operate and expensive to fix. In addition to economic benefits, locally generated solar electricity and thermal energy (mostly in the form of hot water) also cuts the environmental footprint due to the transportation, storage and usage of fossil fuels. Solar electricity generated on-site can also complement the local electricity grids. The generation of local renewable electricity could have very immediate and substantial effects and fundamentally increase energy self-reliance in northern communities. 8

13 Canada s North has an abundant potential for solar energy. The total annual available solar radiation in many northern locations is actually very comparable to large southern urban centers (details see section 2.2). A key challenge pertaining to solar utilization in the North is the strong seasonal pattern near the Arctic (e.g. long daylight hours in the summer and almost no sunlight in the winter when space heating energy load is the highest). Therefore, for northern housing applications, solar systems cannot stand alone and will always need back-up from either on-site or local utility sources. With rising fuel prices and more competitive costs for solar systems, renewable technologies are gaining traction as they become more economically viable. The use of solar energy can be materialized in many different ways, including passive solar house design, photovoltaic, and solar thermal (hot water and space/ventilation heating). For economic feasibility analysis at the different locations (Seifert, 2005), caution should be taken as both energy price and the cost of solar technologies may be subsidized and may not reflect the true costs. Furthermore, future energy prices may also change very quickly. Understanding the costs of energy, and of renewable energy systems, is critical to fully assess the economic viability of solar technologies for any given application in the North. 9

14 2 CLIMATE CONSIDERATIONS FOR THE NSH LOCATIONS 2.1 Location There are four NSHs located across northern Canada (Figure 2.1). The Dawson E/2 NSH, completed in 2008, and the Dawson E/9 NSH, completed in 2009, are both located in the same neighbourhood in Dawson City (64ºN), Yukon. The Inuvik NSH, completed in 2011 is located in Inuvik (68ºN), Northwest Territories. The Arviat NSH, completed in 2013 is located in Arviat (61ºN), Nunavut. Figure 2-1: Geographical location of the four NSHs. Ottawa (45 N) is shown for reference of latitudes. Credit: (Natural Resources Canada) Table 2-1: Climatic and building information for the four NSHs. Name Location Type Dawson E/2 NSH Dawson E/9 NSH Inuvik NSH Arviat NSH Dawson, YT Solar hot water Single n/a n/a Solar PV Latitude, Longitude N, W Heating degree days 1 Annual solar radiation 2 Average annual wind speed MJ/m 3.12 Dawson, 2 flat-plate N, Duplex n/a YT panels W 4 flat-plate 3.6 kw N, Inuvik, NT Duplex panels (8 panels) W Arviat, N, Single n/a n/a MJ/m NU W As a point of comparison, Ottawa has 4500 HDD and 15.8 MJ/m 2 available solar radiation, wind speed of m MJ/m MJ/m Degree days below 18 C (National Research Council of Canada, 2010) 2 Annual solar radiation for South-facing, and tilt = latitude - 15 (Natural Resources Canada, 2013) 3 Average wind from (Natural Resources Canada, 2010) (Arviat not from (Environment Canada, 2003) 10

15 2.2 Solar Radiation Contrary to common perception, the annual available solar radiation in northern Canada is comparable to the solar potential in southern urban centers in Canada (Table 2.1). Figure 2-2 below illustrates the maps of mean daily global solar isolation (MJ/m 2 ) across Canada. Figure 2-2: Mean daily global annual solar radiation map of Canada. Left: Tilt=Latitude; Right: Tilt=Vertical. Credit: (Natural Resources Canada, 2013). Figure 2-3 illustrates the effect of changing the orientation of surfaces at tilt = 75. Not surprisingly, southfacing surfaces have the best overall solar potential. It is also interesting to note that being off south by as much as 15º does not have a significant impact on seasonal or annual solar availability. However, being off south by more than 15º has an increasingly significant effect, reducing the solar radiation received by the surface, particularly during the spring/fall months. Two sources of solar radiation data on tilted surfaces are RETScreen (Natural Resources Canada, 2010), and NRCan PV maps (Natural Resources Canada, 2013). The radiation on a tilted surface is calculated using different assumptions and different time steps. The PV maps use hourly calculations, and is likely more accurate for northern locations where snow reflectance and diffused light play an important role. However, the PV maps are restricted to south-facing surfaces and to prescribed tilt angles only. RETScreen uses monthly calculations, however, tilt and orientation can be customized. For comparative analysis for the NSH projects, RETScreen was used for its flexibility. As shown in Table 2-2 below, the annual solar potentials for the three northern locations are comparable to the southern reference location (i.e. Ottawa). Generally speaking, to maximize the solar potential, an equator-facing orientation is optimal (south-facing in the northern hemisphere). The optimum tilt angle of solar panels is generally given to be equal to the site s latitude for maximum annual output (Hussein, Ahmad, & El-Ghetany, 2004). However, some researchers argue that for high latitude locations, the winter solar radiation can only contribute marginally to the total collectible energy year-round and therefore a fixed solar collector should be oriented to receive maximum light during the summer peak solar energy period of the location in consideration (Rönnelid, Perers, & Karlsson, 1996). 11

16 Table 2-2 Summary of available annual global solar radiation for the NSH locations & Ottawa. Data source: RETScreen International (Natural Resources Canada, 2010) Latitude Annual Global Solar Radiation (MJ/m 2 ) Location (Province/ Territory) South-facing Tilt = Latitude South-facing Tilt = Latitude-15 o South-facing Tilt= Vertical Ottawa (ground data) 45º (ON) Dawson City (NASA data) 64º (YT) Inuvik (ground data) 68º (NT) Arviat (ground data of closest location, Chesterfield Inlet, NU) 61º (NU) The annual solar radiation values in Table 2.2 were obtained from RETScreen. The radiation on a tilted surface is calculated from global horizontal solar radiation, either from ground weather station data or from NASA s global satellite data. The radiation on a tilted surface is calculated using certain assumptions about diffused content of sunlight and the ground reflectance on a monthly basis. Figure 2-3: Effect of changing orientation on monthly solar radiation. Data source: RETScreen (Natural Resources Canada, 2010) Figure 2-4 below illustrates the effect of changing the tilt angle of south facing surfaces on a monthly basis. Note that changing tilt angle from 60º, to 75º, and 90º results in little difference in the winter solar potential when there is less solar energy to recover anyway. However, a steeper slope penalizes the available summer solar potential and leads to a lower annual available radiation. 12

17 Figure 2-4: Effect of changing tilt on monthly solar radiation. Data source: RETScreen (Natural Resources Canada, 2010) Even though a steep tilt angle will penalize the high summer sun and thus reduces the annual solar radiation, steep angles are good at harnessing reflected sunlight from the snow (albedo 1 >0.8) in early spring and late fall which enhances the system performance. This effect is partly taken into consideration in Figure 2.4. RETScreen assumes a ground albedo of 0.2 if the average monthly temperature is greater than 0 C, 0.7 if it is less than 5 C, and uses a linear interpolation for temperatures between 5 C and 0 C. The amount of global solar radiation received by a surface can be broken down into two components, diffuse and direct light. The proportion of diffused radiation calculated in RETScreen uses a general theoretical model developed by Duffie & Beckman (Duffie & Beckman (2006)). However, for high latitude locations, the sunlight has to travel much further in the atmosphere before reaching the ground. Therefore, northern locations typically have a larger than expected portion of diffused radiation, due to the high incidence angle (nearly horizontal) and significant snow/ground reflection. This means that simply setting tilt angle close to latitude is less optimal for maximizing the annual solar availability for the North as a larger proportion of the light is diffused and is coming from all angles. Therefore, determining the optimal tilt angle to maximize solar potential for northern locations is not a straight forward task. For building integrated solar components in northern locations, latitude or latitude less 15 tilts are not feasible for most roof construction, and a steeper roof would create a larger attic than necessary, a larger surface area for heat loss, and would require more building materials that are expensive to bring in and erect. For practical applications, either tilting at a reasonable roof angle of latitude less 15º or lower, or tilting on near-vertical awnings or vertical façades are all possible options. 1 Albedo is a measure of the reflectivity of the earth's surface, defined as the fraction of solar energy (in shortwave radiation) reflected from the Earth back into space. 13

18 Ease in construction and maintenance may justify some loss in collectible solar energy due to nonoptimal tilt, especially for northern remote locations where labor is expensive and it can take a long time to fix damaged systems. Figure 2-5 presents the monthly available solar radiation on a surface tilted to latitude less 15. Compared to Ottawa, the three northern locations exhibit high output between March to June, but little to no winter solar radiation. The panels (PV and solar thermal) are also more likely to be covered by snow in the winter, and a cleaning in the spring is necessary to clear snow to enable solar energy capture. Figure 2-5: Monthly available solar radiation of the NSH locations compared with Ottawa. Data source: RETScreen (Natural Resources Canada, 2010) 2.3 Other Climate Effects Aside from the amount of solar radiation available for a given northern location, many other climatic factors will also affect the performance of passive or active solar components. The outdoor temperature affects the performance of both the photovoltaic and solar thermal system. Typical photovoltaic efficiency increases slightly with lower temperatures whereas the solar thermal output decreases with lower temperatures due to greater heat loss to the cold outdoors. Sizing and selection of windows are also affected by the outdoor temperature, to take advantage of the passive solar gains while still functioning as an effective insulated envelope. 14

19 Figure 2-6: Monthly outdoor temperature of the NSH locations compared with Ottawa. Data source: RETScreen (Natural Resources Canada, 2010) Snow can significantly affect the performance of solar systems. Panels mounted on shallow angles tend to accumulate snow or ice, which reduces the system performance if no cleaning is performed regularly. Strong wind could shed snow from the panel or cause snow drift that buries the system. For solar thermal installations, wind increases the rate of convective heat loss and can significantly reduce the system efficiency. On the other hand, as previously shown, snow on the ground can reflect up to 90% of the incident sunlight on the horizontal plane and therefore enhances the performance of vertically mounted systems or systems with a steep tilt. In short, many parameters that affect potential solar availability for a given system, such as cloud coverage, dirt or snow on solar panels, duration of snow on ground and proximity of other structures, are often difficult to quantify for a given location. 15

20 3 SOLAR POTENTIAL FOR THE NSH HOUSES 3.1 Dawson E/2 NSH House Design The Dawson E/2 NSH is a one-storey, 141 m 2 (1,519 sq. ft.) residential structure completed in early It is located in C4, a Tr ondëk Hwëch in subdivision just south of Dawson. The house was designed and built by the Tr ondëk Hwëch in First Nation, with the support of CMHC and the Yukon Housing Corporation (YHC). It was erected by Han Construction, the local construction company of the Tr ondëk Hwëch in First Nation. The intent of this NSH design and construction was to create a prototype for, and to promote the construction of, northern housing that is both highly energy efficient and culturally acceptable to the occupants and the community. The design goal for this house was to exceed the Model National Energy Code of Canada for Houses (MNECH) (National Research Council of Canada, 1997) by 50%. For more information on the design of the house, see Tr ondëk Hwëch in Northern Sustainable E/2 House Design, Construction and Performance Monitoring Summary Report (Canada Mortgage and Housing Corporation, 2013). Figure 3-1: Floor plan of the Dawson E/2 NSH. Source: CMHC Building Description- E/2 Dawson City Type: New construction, single detached, 1 storey, 3 bedroom Floor space: m 2 1,519 ft 2 Building axis: East-West Building footprint: m 2 1,600 ft 2 16

21 Appearance Figure 3-2: Dawson E/2 NSH south elevation. Credit: CMHC Figure 3-3: Dawson E/2 NSH west and north elevation. Credit: AEA Roof Orientation & Slope The building axis of the Dawson E/2 NSH runs 15 from East-West, with one roof face oriented near south. The roof has a pitch of 5:12 or 22.6 and has an available area of 110 m 2 on each side. N Figure 3-4: Orientation of Dawson E/2 NSH roof. Figure 3-5: Pitch of Dawson E/2 NSH roof. 17

22 Existing Solar There are no active solar technologies on the Dawson NSH E/2. The house is designed with an eastwest axis to provide a southern orientation to take advantage of passive solar gains in the winter. Solar heat gains in the summer are reduced by the 600 mm (24 inch) roof overhang. Solar Potential Table 3-1 summarizes the effect of various orientations and rooftop tilt angles on the available annual solar radiation for the Dawson E/2 NSH as calculated by RETScreen. The base design (100%) was selected using the current Dawson E/2 NSH orientation and roof tilt, where future solar systems (PV or thermal) could be mounted without altering the building. Theoretically, by tilting the solar panels to 49, the annual solar radiation available would increase by 10% as compared to the base design. It is clear that the optimal orientation for solar is due south, however, being off south within 15 does not have a significant impact on annual solar again (less than 1%). Orienting the roof slope to face east or west would result in a decrease of about 30% from the optimal orientation and tilt. Optimization Table 3-1 Available annual solar radiation for various orientations and tilt angles. Variation given in percentage difference compared to original Dawson E/2 NSH. Data source: RETScreen (Natural Resources Canada, 2010) Tilt angle Orientation of the integrated solar system (5:12) 64 (latitude) 49 (lat - 15º) South - facing 100.6% 108.6% 110.4% 15 east or west of South 100.0% 107.6% 109.2% 30 east or west of South 98.2% 104.3% 106.4% 60 east or west of South 91.1% 92.7% 95.1% East or West 81.3% 76.5% 79.5% Potential design scenarios to enhance the capture of solar energy of the Dawson E/2 house were explored using the RETScreen tool. Not all tilt angles for the Dawson E/2 NSH are realistic for buildingintegrated solar installations. Table 3-2 summarizes the annual available solar radiation for the proposed scenarios. All the areas are calculated with a factor of 90% to account for panel framing and other factors. Solar radiation data used for Table 3-1 and Table 3-2 are from the RETScreen climate data base, using NASA's global satellite/analysis data, as ground monitoring weather station data is not available for Dawson city. As shown in Table 3-2, the new build design #2 is not quite realistic as it would be much more expensive to construct, even though its potential solar yield is high as shown in Table 3-2. There could be racking installed on the roof that allows the solar panels to be elevated to the desired tilt angle without changing the roof pitch, although wind loads and general aesthetics would need to be considered and the available area is reduced with a steeper tilt. Design options similar to new build design #3 make more sense if it were a new build. 18

23 Table 3-2 Summary of different design scenarios for Dawson E/2 NSH solar integration. Description Retrofit of current-build New build design #1 New build design #2 New build design #3 Existing orientation and roof angle, add panels to cover the roof Orient main roof face to south facing, keep same roof angle Orient main roof face to south, change roof angle or rack panels to optimal angle Orient main roof face to south, change roof angle to maximum reasonable for roof-integrated panels Tilt Original roof 22.6 (5:12) N Original roof 22.6 (5:12) N Modified roof 49 (latitude-15 ) N Modified roof 30.3 (7:12) N Orientation of roof slope face Available area on main roof Average daily radiation available Annual total radiation available on surface 15 Off South South facing South facing South facing 99 m 2 99 m m m kwh/m 2 /day 3.29 kwh/m 2 /day 3.61 kwh/m 2 /day 3.43 kwh/m 2 /day 91% of max 91% of max 100% of max 95% of max 1295 MJ 1303 MJ 2079 MJ 1420 MJ 19

24 3.2 Dawson E/9 NSH House Design The Dawson E/9 NSH house is a one-storey residential duplex and consists of two unique dwellings completed in It is located in C4, the Tr ondëk Hwëch in subdivision just south of Dawson. The east side dwelling is a 2-bedroom, 120 m 2 (1,300 ft 2 ) Flex house with a covered deck which at a later time can easily be converted into additional rooms or storage. The west side dwelling is a 3 bedroom, 140 m 2 (1,500 ft 2 ) unit. The house was designed and built by the Tr ondëk Hwëch in First Nation, with the support of CMHC and the Yukon Housing Corporation (YHC). It was erected by Han Construction, the local construction company of the Tr ondëk Hwëch in First Nation. The design goal for this house was for the 3 bedroom unit to use 1/9 th the energy (89% less energy) compared with a similar house built to the MNECH (National Research Council of Canada, 1997). For more information on the design of the house see Design and Construction of the Northern Sustainable E/9 Houses report (Canada Mortgage and Housing Corporation, 2010). Figure 3-6: Floor plan of the Dawson E/9 NSH. Source: CMHC Building Description- Dawson E/9 NSH Type: New construction, duplex, 1 storey, 3 bedroom & 2 bedroom flex Floor space (duplex): m 2 1,494ft 2 Building axis: South-North Building footprint (duplex): m 2 1,618 ft 2 20

25 Appearance Figure 3-7: Dawson E/9 NSH south and west elevation. Credit: AEA Figure 3-8: Dawson E/9 NSH west elevation. Figure 3-9: Dawson E/9 NSH east elevation. Roof Orientation & Slope The building axis of the Dawson E/9 NSH runs 5 from north-south with the roof faces oriented near-east and near-west. The roof has a pitch of 4:12 (18 ) and has an available area of approximately 180 m 2. The porch roof is 21:12 (60 ) and has a current available area of 12 m 2. N Figure 3-10: Orientation of Dawson E/9 NSH roof. Credit: Google Earth Figure 3-11: Pitch of east-west facing roof. Credit: CMHC Figure 3-12: Pitch of south facing porch. Credit: CMHC 21

26 Existing Solar Systems The Dawson E/9 NSH utilizes solar hot water and a back-up electric water heater for its water heating. The solar hot water system consists of 2 flat plate collectors mounted on the 60, south-facing porch roof with a storage tank and circulation pump located in the utility room. Performance data on the solar system is provided in Appendix A. The building is oriented with its long façade facing south. Large windows on the south façade and smaller ones on the east and west admit passive solar energy and natural lighting into the living and dining areas. Small windows on the north admit light to the bedroom while minimizing heat loss. Solar thermal gain is limited in Dawson during the winter because the entire town is in a valley and receives no direct sunshine for much of the winter. Figure 3-13: Two-panel solar hot water system on Dawson E/9 NSH porch roof. Credit: Saskatchewan Research Council Figure 3-14: Solar hot water storage tank. Credit: AEA Solar Potential Table 3-3 summarizes the effect of various orientations and tilt angles on the available annual solar radiation for the Dawson E/9 NSH. The base design (100%) was selected using the existing orientation and porch roof tilt angle, where two solar hot water panels are currently mounted. As the system is already south facing and close to optimal tilt, the changes in orientation and tilt angle potentially would result in less than 1% increase of the annual incident radiation per unit area. Compared to the existing 60 tilt, panels at 49 (latitude -15 ) would result in a higher summer output and slightly more available awning area. Orientation of the integrated solar system Table 3-3: Available annual solar radiation for various orientations and tilt angles. Variation given in percentage difference compared to original Dawson E/9 NSH. Tilt angle 18.4 (4:12) 22.6 (5:12) 49 (lat - 15º) 60 (21:12) Awning 90 (Vertical) South - facing 89.1% 91.9% 100.8% 100.0% 85.2% 15 east or west of South 88.8% 91.3% 99.7% 99.2% 84.4% 30 east or west of South 87.2% 89.7% 97.2% 96.1% 81.8% 60 east or west of South 81.8% 83.2% 86.9% 85.5% 72.6% East or West 74.3% 74.3% 72.6% 70.7% 60.3% 22

27 Table 3-3 also indicates that if solar systems were to be installed on the vertical façade directly, instead of on the 60º awning, there will be a reduction of 15% of the potential solar radiation per unit area. Though better at harnessing reflected lights, vertical panels receive less direct sun in the summer, and the winter sun only contributes minimally towards the annual solar gain. The porch roof also provides shading for the windows underneath during the summer months and serves as an ideal place for solar integration on the current Dawson E/9 NSH. Optimization The current solar panels are installed on the 60 porch roof on the south facing façade, while the main roof currently facing east-west could accommodate more solar if the building (or roof) were to be rotated by 90 (i.e.; to have the main roof area facing south). Potential design scenarios are explored using the RETScreen tool. Table 3-4 summarizes the available solar radiation (per unit area and annual total) for the proposed scenarios. The total available areas for porch roof and main roof are calculated with a factor of 90% to account for panel framing and other factors, assuming that panels of various sizes will cover the entire available area. The retrofit current-build option could be implemented without significantly altering the building design. Using all the available façade area to incorporate a larger porch roof, it can quadruple the existing solar capacity. The three new build design options would require rotation of the whole building (or the roof structure) by 90 to have the main roof facing south. This change alone will result in more than 11 times more available solar capacity due to the increase in available south-facing area. While new build design #1 and #2 remain feasible in terms of the roof pitch, design #3 is less realistic as it results in more unusable attic or space and would likely be more expensive to construct. Other possibilities include a rack-mounted system on the shallow roof to increase the tilt angle, and ground mounted systems that are independent from the building itself. Ground mounted solar systems have the advantage that they can be placed anywhere and at any angle free from shading. However, vandalism may be a concern. Rack-mounted systems on roofs are not as subjected to vandalism, but drastically change the look of a house. Rack mounted installations, when angled more than the roof slope, may be more prone to damage from wind uplift, snow drift, and moisture issues at the interface of the rack and the roof. 23

28 Table 3-4 Summary of different design scenarios for Dawson NSH E/9 solar integration. Data source: using RETScreen (Natural Resources Canada, 2010) Description Currentbuild 2 solar hot water panels on the south facing 60 porch roof Retrofit of current-build Increase area of porch roof and add more panels to cover the available area New build design #1 New build design #2 New build design #3 Orient main roof face to south, keep the existing roof slope at 4:12, install panels to cover the available area Orient main roof face to south, change roof slope to 7:12, install panels to cover the available area Orient main roof face to south, change roof slope to resemble a barn roof of 45 and 18.4, install panels to cover the available area Tilt Original porch roof 60 Original porch roof 60 N N Existing roof 18.4 (4:12) Modified roof 30.3 (7:12) N N N Modified roof 45 and 18.4 Orientation of roof slope face Available area on main roof Average daily radiation available Annual total radiation available on surface 4 5 east or west of South 5 east or west of South South facing South facing South facing 11 m 2 (2 panels) 3.58 kwh/m 2 /d 100% of max 43 m 2 (8 panels) 3.58 kwh/m 2 /d 100% of max 142 m m 2 52m2 at 45 ; 104m 2 at kwh/m 2 /d for 45 ; 3.19 kwh/m 2 /d 3.43 kwh/m 2 /d 3.19 kwh/m 2 /d for % of max 96% of max 39 MJ 155 MJ 454 MJ 537 MJ 518 MJ 100% & 89% of max 24

29 3.3 Inuvik NSH House Design The Inuvik NSH is a one-storey duplex built with an open concept design and was completed in The entire duplex is 247 m 2 (2,656 ft 2 ) with two 119 m 2 (1,277 ft 2 ) suites and a shared 9.5 m 2 (102 ft 2 ) mechanical room. The Inuvik NSH is a demonstration project by the Northwest Territories Housing Corporation (NWTHC), with support from CMHC and is operated by the Inuvik Housing Authority (IHA). This demonstration project was intended to design, construct and monitor a house in the NWT that is highly energy efficient, healthy to live in, culturally appropriate, and one whose design and components can be implemented in other northern houses in a cost-effective manner. The NWTHC set and achieved a design objective to meet an EnerGuide for Houses (EGH) rating of 85. For more information about the design and construction of the NSH Inuvik, see Design and Construction of the Inuvik Northern Sustainable House report (Canada Mortgage and Housing Corporation, 2013). Figure 3-15: Floor plan of the Inuvik NSH. Source: NWTHC Building Description- Inuvik NSH Type: New construction, duplex, 1 storey, 3 bedroom Floor space (for duplex): m 2 2,316 ft 2 Building axis: Southwest-Northeast Building footprint (duplex): m 2 2,656 ft 2 25

30 Appearance Figure 3-16: Inuvik NSH southeast elevation. Credit: AEA. Figure 3-17: Inuvik NSH southeast and northeast elevations. Credit: CMHC. Figure 3-18: Inuvik NSH northeast elevation. Credit CMHC. Roof Orientation & Slope The building axis of the Inuvik NSH runs 40 from east-west with the roof faces oriented southeast and northwest. The southeast roof/overhang has a pitch of 75 and has an available area of approximately 36 m 2. N Figure 3-19: Orientation of the Inuvik NSH roof. Credit: Google Earth. Figure 3-20: Pitch of southeast and northwest facing roofs. Credit: NWTHC. 26

31 Existing Solar Systems The hot water used in the duplex is pre-heated by four glazed flat-plate solar collectors. A double-wall heat exchanger transfers the heat gathered by the fluid circulated through the collectors to a 120 gallon storage tank. The pre-heated water flows to a domestic hot water tank where it is further heated via a loop from the boiler as needed. Each housing unit has eight 224W solar photovoltaic modules installed at 75 tilt directly resting on the roof with a total nameplate capacity of 1,792 Watts per unit. A grid tie inverter converts the direct current power to alternative current. The solar-generated electricity is first consumed by local loads within the house, and the excess generation is fed back into the grid where it is measured by a separate meter. The excess electricity generated is credited to the Local Housing Authority following a net billing program and the credits are used to offset the monthly electric bill. Performance data for the solar systems is provided in Appendix A. The building is oriented with its longer front elevation facing southeast. Large windows on the southeast admit passive solar energy and natural lighting into the living and dining areas. Small windows on the northwest admit light to the bedrooms while minimizing heat loss. The overhang on the southeast facade reduces solar heat gain in the summer. Figure 3-21: Solar hot water panels on roof of Inuvik NSH. Credit: NWTHC Figure 3-22: Large hot water storage tank for solar heated water for Inuvik NSH. Credit: AEA Figure 3-23: PV on the roof of Inuvik NSH. Credit AEA Figure 3-24: Inverters for the PV on Inuvik NSH. Credit AEA Solar Potential Table 3-5 summarizes the effect of various orientations and tilt angles on the available annual solar radiation for the Inuvik NSH. The base design (100%) was selected using the current Inuvik NSH 27

32 orientation (35º south-east) and roof slope (75º) where the current solar panels (electric and thermal) are mounted. According to the analysis performed using RETScreen with ground weather station data for Inuvik, Table 3-5 indicates that orienting the house to due south will increase the available annual solar radiation by 6%. Table 3-5: Available annual solar radiation for various orientations and tilt angles. Variation given in percentage difference compared to original Inuvik NSH. Data source: RETScreen (Natural Resources Canada, 2010) Tilt angle Orientation of the integrated solar system 45 (12:12) 60 (21:12) 75 (awning) 90 (Vertical) South - facing 108.1% 109.9% 106.0% 97.0% 15 east or west of South 106.9% 108.7% 104.8% 96.1% 35 east or west of South 102.7% 103.6% 100.0% 91.9% 60 east or west of South 92.8% 92.8% 89.2% 82.0% East or West 76.9% 75.7% 72.4% 67.0% A 10% increase can be achieved if the house is facing south and the tilt angle is lowered to 60º. Optimization The existing solar panels are mounted at 75 on the main roof. There are also two side roofs set back from the main roof that could accommodate more solar; but they would be partly shaded during the day. Potential design scenarios were explored using the RETScreen tool. Table 3-6 summarizes the available solar output for the proposed scenarios. The total available areas are calculated for roofs at different angles, with a factor of 90% to account for panel framing and other factors, assuming that the entire available area will be covered by panels of various sizes. Decreasing the roof angle where the solar panels would be mounted would increase the available potential area for panels, but will also provide more shading to the south facing windows and thus less passive solar gains will be available to offset space heating. By using both the main roof and the side roofs, orienting the house to face south, and decreasing the roof angle to 60º, new build design #2 is close to optimal and would lead to 1.6 times more solar potential (MJ/year) than the current build. Ideally, the side roofs could be designed so that they are not shaded by the main roof during parts of the day. If shading on the side roofs is inevitable, solar domestic hot water (SDHW) panels should be put on the side roofs instead of photovoltaics, as the thermal output is directly proportional to the unshaded panel area. Partial shading on PV systems reduces the entire array output as the overall output is determined by the PV cell with the lowest output. This problem can be addressed by using micro-inverters on each individual PV panel instead of using one inverter for the entire PV array. 28