Highlights

• Rooftop solar power can meet up to 20% of a hospital’s electricity requirements in India.
• If your hospital consumes a lot of diesel for power generation, rooftop solar can abate your diesel bills, subject to timing of load shedding.
• 100 SF of shade-free rooftop space can provide 4 kWh of solar power per day, on average.

Overview

Hospitals both in urban and rural areas consume a lot of energy throughout the day as the electrical equipment used directly or indirectly to treat patients require uninterrupted power. Many hospitals have considerable unused rooftop space. Combined with power shortages and rising cost of diesel, rooftop solar power makes a compelling case for implementation in hospitals.

Advantages

• Energy security – Rooftop solar plants can deliver power during load-shedding, ensuring that critical loads are always running.
• 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). Additionally, your energy cost is now fixed for the next 25 years, unlike diesel 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.

Typical Load

As the rooftop space may not be sufficient to support the entire electrical load of your facility with solar, it becomes necessary to estimate the different kinds of loads to identify loads that can be/need to be supported by solar.

Electrical loads are estimated by calculating the wattage or amperage of electrical equipment in use, which can be further classified as light loads and heavier loads, with solar being used to support the light loads.

Typical electrical loads in a hospital include

• Lighting
• Fans
• Refrigeration units
• Other electrical equipment
• Air conditioning

Air conditioning is usually the heaviest load in hospitals, accounting for more than half the energy consumed. Air conditioning is not a critical load in many companies; Hospitals, however, may have some air conditioning load, such as in operation theatres or ICUs, where air conditioning has to run even during load shedding.

Our Recommendation

The need for uninterrupted, constant power and possibly limited roof space necessitates rooftop solar power being used in conjunction with other sources of power such as utility power, diesel generator, and/or batteries.

Based on the unique needs and constraints faced by hospitals, Balaji Solar Solutions recommends :

Alternative 1 –With clear separation of loads

Where it is possible for some loads (typically the lighter loads) in the hospital to be isolated and fed using a dedicated feeder, the following architecture can be used

• Powering some critical loads – When combined with a battery bank, a solar plant can be used to reliably support some critical loads; which critical loads can be decided in consultation with the hospital’s infrastructure team. In the event of a power failure these loads will be supported by solar power and the battery bank will compensate for any deficiency in solar power at that time
• Battery backup – The battery bank will be charged by solar power, and will support critical loads of the hospital for short durations during the daytime when solar output may be reduced. Night time support is also possible, depending on the size of the battery bank
• Battery sizing decides the duration of battery backup available. Batteries add significantly to the cost of the project, need to be replaced every few years, require maintenance, and impose weight and space requirements. Therefore we recommend limiting the battery bank to about an hour of backup
• Hybrid inverter – A rooftop solar PV system that utilises a hybrid inverter will allow the solar plant to integrate with a diesel generator. Here the rooftop solar plant serves to reduce diesel bills by supporting part of the load
• Integrating a rooftop solar plant with a diesel generator involves several challenges that need to be overcome with careful design and sizing of the rooftop solar plant

Alternative 2 – Without clear separation of loads

If it is not possible to isolate critical loads through a dedicated feeder, the solar power will have to be fed along with the diesel generator/EB power to the entire facility. Such a plant will contribute to savings in diesel, but support to specific loads in the event of a power failure will not be provided.

This configuration also require a hybrid inverter, but batteries will not be required. It should be noted that in the event of a power failure, if the DG is shut down the solar plant will also shut down. 

For either alternative, we recommend net metering to ensure that excess solar generation, if any, is monetised.