The Community Property Fund currently has grid-tied rooftop solar plants installed in two of its shopping centres in Gauteng: Alexandra Plaza (October 2018) and Heidelberg Mall (December 2018). The next solar projects are planned for Gateway Mall in Gauteng and Kuyasa Centre in the Eastern Cape.
An initial assessment was done to determine which shopping centres in the Fund’s portfolio would be considered for solar installations from an energy yield and financial benefit perspective. All shopping centres in the portfolio were then ranked based on the following criteria:
- Location on the Global Horizontal Irradiation (GHI) solar map: This map refers to the amount of radiation received in an area, measured in kWh/m² and is critical to photo-voltaic This is shown in the graphic below.
- The effective cost of electricity per kilowatt-hour (R/kWh): Tariffs applicable to standard time periods were used as the effective cost per kWh where centres are billed on a time of use (“TOU”) electricity tariff.
- Local supply authority: It needs to be noted that solar installation contractors are currently experiencing difficulties receiving authorisation from Eskom to commission grid-tied solar systems.
Feeding back into the grid
Most municipalities are in favour of consumers feeding back into the local grid as the municipality is then essentially receiving free electricity. There are a handful of municipalities that pay a net-metering tariff, meaning that the consumer is reimbursed for all energy that is fed back into the grid. At this stage, the only building in the Fund’s portfolio that can take advantage of this is Motherwell Centre, which falls under the Nelson Mandela Municipality.
Layout and design
A lot of time was spent on the layout design of the solar modules, accounting for movement of the roof sheeting and additional load bearing. The shadows around the vents were analysed in detail and areas where shadows are cast (in summer and winter) were specifically avoided in the layout. Click on this link [link to video] for a view of the installation at Alexandra/Heidelberg [I’m not sure which].
The investment that the Fund has made in SMART metering over the past few years gave solar contractors the tools to plan the energy load for every half an hour of each day for a period of one year, allowing them to build precise profiles and understand winter/summer trends. By accurately plotting the load profile for the buildings, the risk of overcapitalisation is reduced and solar potential is maximised.
Solar photovoltaic modules
Polycrystalline solar photovoltaic modules were chosen for the installations the following reasons:
- polycrystalline technology has the widest use and therefore is the lowest risk;
- physically large modules lead to a high wattage per module which reduces mounting structure and installation complexity;
- modules are certified to withstand wind load and 35mm hailstones at 97km/h;
- advanced glass and surface texturing allows for excellent performance in low-light environments;
- the modules have high salt mist and ammonia resistance; and
- the improved temperature coefficient decreases power loss during high temperatures.
A walkway was installed in between the panel rows, protecting roof sheeting during installation, maintenance and cleaning.
Savings for the Community Property Fund
The installation at Alexandra Plaza was completed in October 2018, and the one at Heidelberg Mall in December 2018. The total capacity to date is 2.2 megawatt peaks (MWp), estimated to generate 3.5 million kilowatt hours (kWh) in the first year of operation.
Both installations are optimally designed to significantly reduce the municipal power consumption at the shopping centres. Since completion, the Alexandra and Heidelberg solar plants have out-performed their initial design parameters, achieving financial savings of R719k for the first quarter of 2019. With the current generation and performance, the estimated yields (year one returns) on these projects are: 20.35% at Alexandra and 19.90% at Heidelberg. This excludes the electricity tariff increase of 13.8% on 1 July 2019. The financial benefit of the solar installations accrues to the Fund. The Fund incurs the capital expenditure and obtains a return on its investment by supplying electricity to tenants at a margin over the cost price.
The installations benefit the environment and therefore the local community with their lower carbon footprint, by using a renewable energy source as opposed to traditional electricity sources such as Eskom’s coal-fired power stations which are harmful to the environment.
Definitions and Abbreviations
Irradiance - Solar irradiance is the energy per unit area received from the sun in the form of electromagnetic radiation.
kWh - Kilowatt hour is a composite unit of energy equivalent to one kilowatt (1 kW) of power sustained for one hour.
kWp - Kilowatt peak stands for peak power. This value specifies the output power achieved by a solar module under full solar radiation (under set Standard Test Conditions). Solar radiation of 1 000 watts per square meter at 25 degrees Celsius is used to define standard conditions.
PV - Solar cells, also called photovoltaic cells, convert sunlight directly into electricity. It is the process of converting light (photons) to electricity (voltage), which is called the PV effect.
DC – Direct Current - The unidirectional flow or movement of electric charge carriers (which are usually electrons). The intensity of the current can vary with time, but the general direction of movement stays the same at all times.
AC – Alternating Current - The flow of electric charge that changes direction periodically. As a result, the voltage level also reverses along with the current. In a 50Hz system such as those used in South Africa, this equates to current direction changing 50 times a second. AC is used to deliver power to houses, office buildings, etc.