Solar for Shopping Malls

Overview

In India, rooftop solar energy can supply 15–25% of a shopping mall’s electricity needs.
Depending on when load shedding occurs, rooftop solar can reduce your diesel bills by up to 20% if your retail center uses a lot of diesel for power generation. On average, 100 square feet of shade-free rooftop area can generate 4 kWh of solar power per day.

Shopping malls are large energy consumers in cities: they function for 12 hours a day or more, are typically fully air conditioned, and feature a great deal of lighting even during daytime. With abundant rooftop space both in the mall buildings and in parking areas they are ideal candidates for solar power. There are some constraints, however, in using solar power that should also be considered; both are discussed below.

Advantages

  • Energy security – Rooftop solar plants can deliver power during load-shedding, ensuring that critical loads are always running
    • Not all solar plant configurations can deliver power during load-shedding. More details here
  • Cost-effective –Rooftop solar power has a levelised cost of Rs. 4.5-5/kWh (or less), considerably lower than diesel power cost at Rs. 18/kWh (or more). Depending on your tariff, solar may even be cheaper than EB power. Additionally, your energy cost is now fixed for the next 25 years, unlike diesel and EB power which keeps increasing
  • Reliable –A solar power plant has no moving parts, ensuring reliable power over 25 years
  • Minimal maintenance –A solar plant requires very little maintenance from the energy consumer
  • Flexible configurations –Solar panels can be installed on different kinds of roofs, including covered parking areas, as long as the structure can bear the weight of the panels. They are also highly scalable, with rooftop plants ranging in capacity from less than 1 kW to more than 1 MW

Constraints

  • Rooftop space – The capacity of the solar plant that can be installed in a mall may be constrained by lack of sufficient shadow-free rooftop space. Roof requirements are discussed in detail here; a rule of thumb is that you will need about 100 SF of shade-free roof area for 1 kW of solar panels. Insufficient roof area will mean that the capacity of the solar plant on your roof may be sufficient to meet only part of your electrical load
    • When estimating available rooftop space, alternative uses for the roof, such as billboards or mobile phone towers, should also be considered as these will not only occupy space on the roof but also cast a shadow that will limit the space where solar panels can be installed
  • Infirm power –Solar power is dependent on the sun shining, and output varies depending on meteorological conditions e.g., passing clouds can temporarily reduce the solar plant’s output. Therefore solar power for critical applications should be used in conjunction with another source of power
  • Daylight power –Solar power is only available when the sun shines. Therefore night time applications will require other sources of power, or power from batteries charged through solar
  • Load-shedding timings: Since solar power is only available during the day, it would not be able to help you reduce your fuel usage if the majority of your load-shedding takes place at night. This could be a problem in certain retail malls because a lot of electricity is only used in the evening.
  • Weight of the inverter: A 100 kW inverter will weigh roughly 1,000 kg but only take up a few square feet of space. This is necessary to convert the DC power output from the solar panels to AC. It could be necessary to locate the inverter on the ground level and use the proper cables to make up for energy loss if the structure is unable to sustain this weight. When designing, building aesthetics and accessibility should be taken into account.

Normal Load

It becomes vital to assess the various types of loads in order to determine which loads can or should be supported by solar, since the rooftop area may not be enough to cover your facility’s whole electrical load with solar.

Electrical loads can be further divided into light loads and heavier loads, with solar power supporting the light loads. Electrical loads are assessed by estimating the watts or amperage of electrical equipment in use (as indicated above).

Typical electrical loads in a shopping mall include

  • Lighting
  • Inside the mall (stores and common areas)
  • Decorative lighting
  • Outdoor lighting
  • Basement parking lighting
  • Air Conditioning
  • Elevators and Escalators
  • Computers
  • Play area
  • Food court
  • Refrigeration units
  • Ovens and stoves
  • Equipment in beauty salons
  • CCTV
  • Other electrical equipment

Our Recommendation

When constructing a rooftop solar system for shopping malls, we have a variety of options to consider due to the large range of electrical loads and their time. Two distinct mall usage scenarios have been defined by Solar Mango, which suggests

Option 1: With the important loads clearly separated When it is feasible to isolate and feed certain vital lighter loads—like security systems or parking lights in basements—using a special feeder, we advise

Certain important loads can be reliably supported by a solar plant when paired with a battery bank; the mall’s infrastructure team can help determine which critical loads need to be supported. These loads will be powered by solar energy in the case of a power outage, and

Battery backup: During the day, when solar production may be lower, the battery bank will be charged by solar energy and maintain vital loads for brief periods of time. Depending on the battery bank’s size, nighttime support is also feasible.
The amount of battery backup time is determined by battery size. Batteries demand upkeep, weight, and space, and thus raise the project’s cost considerably. thus also need to be changed every few years. Therefore, when choosing the battery bank’s size, we advise taking into account both present and future costs as well as space needs.

Hybrid inverter: The integration of a diesel generator with a rooftop solar PV system is made possible by the use of a hybrid inverter. In this case, the rooftop solar plant helps down diesel costs by assisting with a portion of the load. Charge controllers are another element of hybrid inverters that govern battery charging.
A rooftop solar plant’s careful design and sizing are necessary to overcome the various obstacles involved in integrating it with a diesel generator, which are covered below.

How Much Does a Rooftop Solar Plant Cost?

Here is a detailed discussion of the cost of a rooftop solar plant, including incentives and subsidies, and here is a discussion of the returns on switching from diesel to solar power. The typical cost of a 1 kW solar plant that produces 4 kWh of solar electricity per day is approximately Rs. 1 lakh (not counting subsidies, installation fees, and battery costs).

Depending on how much battery backup is needed, batteries may increase the plant’s cost by as much as 30%.

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