Solar Power: Dancing With Physics
June 3, 2015
By Gordon Howell, P.Eng. Howell Mayhew Engineering
The engineer who designed the largest BIPV solar PV system in Canada explains what makes it unique. The array is located at the University of Alberta's Jeanne & Peter Lougheed Performing Arts Centre in Camrose.
From the May 2015 issue, page 28
Engineering design involves the application of engineering principles to both the “big” picture view and the small details of a project. It is somewhat like dancing with physics. It embraces both the flair of art and the bonds of mathematics at the same time — specialized professional judgement informed by numbers.
This interplay between art and physics is readily seen in the use of two revolutionary energy technologies, solar photovoltaics (PV) and light-emitting diodes (LED). Their use is breaking new ground in sustainable building design at the Jeanne & Peter Lougheed Performing Arts Centre on the University of Alberta’s Augustana campus in Camrose, central Alberta. The Centre is a 550-seat theatre, built as a joint initiative between the City of Camrose, Camrose County, the Government of Alberta and the University of Alberta.
The adoption of new technologies comes with a fascinating set of technical challenges, barriers and opportunities, mixed with human emotion and ingenuity. The challenges come from understanding what is needed to design, install and market technologies in applications that have rarely if ever been done before, and from understanding the underlying physics, economics and human psychology that are simultaneously at work. As with any large building, learning institutions have stringent requirements for capital and operating costs and user relationships. Designers and owners are typically more comfortable in specifying and operating well known older technologies. Breaking through barriers to introduce new technologies needs designers and owners who are willing to accept less familiar technologies and demonstrate them to the world.
Integration with flytower cladding
The goals for the PV system at the performing arts centre include both:
• technical goals: reducing electricity operating costs and reducing the building’s environmental footprint
• capacity development goals: gaining experience with the technology on a large building, combined with integrating the technology into the building cladding system, and providing leadership to building owners, consultants and contractors.
Most grid-connected solar PV systems consist of the same basic elements: an array of solar PV modules, PV array mounting racks, grid-dependent DC to AC inverters, wiring, disconnects, signage, design, approvals, procurement, supply, construction, commissioning, operation, monitoring, analysis and maintenance.
This PV system is the largest of about 40 building-integrated (BIPV) systems installed in Canada. A BIPV system is one in which the system’s solar PV modules are integrated into and form part of the building’s wall or roof assembly instead of just being fastened onto an existing assembly. The next largest BIPV system is 86 kW on the flat roof of a building in Toronto.
The Centre’s solar PV array is integrated into the cladding on all four walls of the theatre’s fly tower (facing due south, west, east and north). The PV modules are clamped to two horizontal rails mounted onto vertical Z-girts with insulation fitted between them. If a PV module is removed, then yellow insulation is visible.
A building-mounted grid connected PV system is designed to meet a number of concurrent and competing factors all in one system:
• architectural (aesthetics and available building geometry);
• structural physics (weight, wind and snow)
• electrical physics (electrical characteristics of the PV modules matched to the DC requirements of the inverters throughout a range of PV cell temperatures and levels of solar irradiance)
• financial requirements (project budget, energy generation, energy price, return on investment)
• environmental requirements (emission reductions), and
• legal requirements (grid connection regulations).
As with any design, compromises between these factors need to be made.
The Centre’s solar PV array is configured structurally and electrically as shown in Table 1 (p. 30). Strings of series-connected PV modules are connected to 24 single-phase inverters operating at 208 VAC and rated at 5 kW AC, for a total PV system capacity of 120 kW AC. The solar PV system is expected to generate 80 MWh of electric energy per year, which is 20% of the building’s annual electric energy consumption. Once finalized, the system’s energy performance will be displayed in the building’s foyer and on the internet, and compared with the expectations from modelling. The system commenced operation in June 2014 and was connected to the internet in March 2015. Its actual performance over a year is not known yet.
Design and installation challenges
As happens with most leading-edge projects, challenges were encountered in the design and installation. These challenges are providing valuable information about integrating solar into the building design process, and about solar PV operation on wall surfaces throughout the year. The main technical challenges arose from:
• PV array angles. The PV system is effectively four separate PV systems facing in different directions, each with different generating profiles and operating temperatures throughout the day. The result is they have different electrical design requirements.
• Flashing. Natural ventilation of the PV array was reduced because the PV modules needed to have flashing mounted between them and at the ends of the rows. The flashing was needed so that the yellow insulation behind the modules would not be seen, and to restrict the construction of any bird or insect nests. Increased PV module temperatures reduce power generation slightly.
• Dimensions. The unique building-integrated nature of the PV array required it to fit within tight horizontal wall dimensions. The width of the PV array had to be acceptable both at the time of construction in accommodating PV module manufacturing tolerances, and throughout the year with the expansion and contraction of aluminum mounting rails at temperatures between –45°C and +80°C.
LED theatre lighting and energy savings
Along with generating electricity from solar PV, the building significantly reduces its energy consumption with high-efficiency boilers and chillers, fans with infinitely variable speeds, high levels of insulation — and most notably by using very high-efficiency LED lighting.
The use of LEDs for stage lighting in the theatre is unique and innovative — the Centre broke all kinds of new ground with this lighting. There are no incandescent lights; this is the first theatre in Canada that uses LEDs for its entire house and stage lighting, and it is likely among the first 20 theatres in the world that have lighting based entirely on LEDs.
Theatres have lighting requirements that are much more rigorous and specialized than many other lighting applications. In this case the stage lighting uses next generation seven-colour LEDs, which can change colour and intensity on command. As a result, coloured plastic films (called “gels”) are not needed in front of the lights in order to get the required colour tones and balance. Gels typically need to be replaced after every three hours of use because the large amount of heat generated by standard incandescent lighting bleaches out the colour from the gels. As a result, theatres have two sets of stage lights — one for rehearsals, which are not as bright, and one for performances. Because of LEDs’ cool operating temperatures and their adjustable colour, only one set of stage lighting needed to be designed, purchased and installed in this building.
Furthermore, because of the LEDs’ cool temperatures, the Centre doesn’t require as much building cooling equipment or use as much cooling energy. In addition the lifetime of the LED lights is around 90 times longer than incandescent lights (50,000 hours, or 45 years of life, if used three hours per day, instead of 300 to 500 hours, or six months). All of this adds up to savings in energy, labour and lighting infrastructure. It is estimated that the LED lighting reduced electrical demand from 184 kW to 25 kW and saved more than $100,000 on infrastructure costs alone.
The building earned four Green Globes, the highest level of achievement under the green building certification system. Four Green Globes are awarded to projects that demonstrate national leadership and excellence in energy, water and efficiency to reduce environmental impacts.
The application of these new technologies will yield many years of research, evaluation, presentations and notable leadership for the University of Alberta and its far-reaching “Envision” energy management program, which is now celebrating 40+ years of experience
The Jeanne & Peter Lougheeed Centre for Performing Arts is hosting visits from theatre owners, designers and actors wanting to experience the new theatre. It is a treasure of which the University of Alberta, the City of Camrose and its partners and surrounding community can be very proud. cce
Gordon Howell, P.Eng. is a principal with Howell Mayhew Engineering of Edmonton.
Lougheed Performing Arts Centre, Design Team:
Owner: University of Alberta
Client: University of Alberta and City of Camrose
Solar PV engineering: Howell Mayhew Engineering (Gordon Howell, P.Eng.)
Lighting consultants: Schick Shiner and Associates
Design-builder: Clark Builders
Architecture: BR2 Architecture
Structural engineering: Read Jones Christoffersen
Mechanical-electrical engineering: Smith & Andersen