Building energy consumption accounts for more than a third of India’s total energy consumption. Add to this the fact that more than 70% of the buildings that will stand in India in 2030 are yet to be built. Clearly, making buildings energy efficient, as well as local producers of clean energy, is a priority for the country.
With the falling prices of renewable energy it is now easier than ever to increase clean energy consumption in buildings. However, beyond the initial low hanging fruit (rooftop solar!), the time is right to start venturing into new spaces for increasing onsite clean energy generation.
With the buildings growing vertically in almost all major cities, it is but natural to imagine the growth of solar on this vertical plane!
To be fair, vertical installation of solar PV on buildings has been demonstrated as a technically feasible option for some time now. But with the falling of solar PV prices, this application is seeing a new spurt of growth.
BIPV, as many of you avid readers would know, is an integration of solar PV system into a building’s envelope. Apart from serving as a ‘skin’ to the building, the solar modules can also generate clean power in the process.
With a market share of approximately 1% in the global solar PV market, BIPV is still a niche application. A few years back, the EU-funded PVSites project had estimated that by 2022, BIPV will account for around 13% of the total PV market.
India’s Largest BIPV System
In 2019, U-Solar Clean Energy Solutions Pvt. Ltd. installed India’s largest building integrated vertical solar PV system at a data center in Mumbai. The system, with a capacity of about 1 MW, has been installed by integrating solar panels on all four walls of the facility, covering over 5000 square feet of facade area.
R. Harinarayan, Founder and CEO of U-Solar, shared over an email that,
“By replacing the glass used in the facade with photovoltaic modules we have created a solar power plant on the building structure while the inverter and other components are housed inside the building. As the facility uses electricity 24/7, the BIPV solar plant offsets a part of the carbon emission due to their dependence on fossil fuel based grid electricity – an initiative taken by the data centre to meet their sustainability goals”.
Since this was an existing building, the project came with its own set of challenges.
It called for the use of custom designed aluminum rails as the module mounting structure. Frameless panels were used on the facade. The panels were connected as they were placed on the structure, and electrical work and construction took place simultaneously for timely delivery.
Since the building was already constructed, this was a constraint on the solar energy that could be harnessed. To partially address this issue, power optimizers have been used on each panel.
Power optimizers increase energy output from PV systems by constantly tracking the maximum power point (MPPT) of each module individually. They can also monitor the performance of each module.
In terms of environmental benefits, U-Solar estimates the solar power system will help provide a CO2 emissions reduction equivalent to almost 7000 trees per year.
Advantages Of The Vertical Route
There has been a continued increase in the number of real estate projects opting for green certifications – both LEED and India’s own GRIHA rating systems. This has slowly but steadily opened up a larger market for local energy generation as well as energy efficiency.
Most of the time, however, the roof available for installing conventional rooftop solar systems is quite limited in tall buildings as most of it is used for other purposes as well. The building facade, on the other hand, can provide a much larger space which is otherwise quite unusable for anything else.
This provides an opportunity to replace the conventional glass used in commercial buildings with solar panels which can generate power, thereby reducing its energy footprint in addition to providing a positive ROI on the additional investment.
The panels themselves can act quite like thermal insulation by blocking the sun and thus also reducing the power consumption of the air conditioning system.
Performance Of BIPV Systems
In the case of vertical BIPV systems, a reduced output should be expected as all the panels can not be placed in the optimal direction from a power generation point of view.
The table below shows the output for a small 1 kW system if it were to be installed in different orientations in Delhi (U-Solar’s project location is Mumbai though).
I should add that I did not really consider any special adjustments and that the output tabulated below is purely on the basis of orientation. There might be other factors such as partial shadow, temperature effects etc. that may come into play.
|Solar panel’s tilt relative to the horizontal||Direction of the solar panel||Annual output for a 1kW DC solar system (kWh/year, in Delhi)||Output relative to highest generation (%)|
|Average of all four vertical systems||672||47|
Clearly, the power output is reduced to almost half as a result of the orientation. But what you need to realize is that vertical BIPV really opens up the quantum of local energy generation, and a decision on the viability should be done after evaluating the system’s return on investment (ROI).
For example, in case of U-Solar’s data center project in Mumbai, the facades provide a total area of at least 7-8 times of that available on the roof. And this by the way, is assuming all the roof is empty. Which it is not.
Here’s a look at the actual solar power generation at the site of U-Solar’s installation.
Does The ROI Work Out?
As per Mr. Harinarayan, interestingly, the actual generation at U-Solar’s project site is higher than the simulated estimated generation.
Since this is a first of its kind system for the company, they have been engrossed in evaluating the performance through remote monitoring and intervene in case of deviations from the normal power generation. The learnings will be useful in replicating similar systems.
He added, however, that the output is expected to stabilize closer to the simulated estimation as the modules degrade over time.
Now, the initial cost of BIPV is offset in part due to savings from the reduction in conventional building materials and labor that would have normally been used. Once the solar power system is in operation, there are additional savings from the electricity generated.
The ROI in a BIPV project would be calculated on the incremental investment over what the glass facade itself would cost.
Typically, the payback period for a solar power plant is calculated based on the generation of the BIPV system over 25 years. If you consider the life of the building as 50-100 years, clearly this is significantly less, and perhaps the BIPV system may need several replacements. But that by itself shouldn’t be an issue.
The payback of a typical rooftop solar system in India is 3-4 years for commercial consumers. Going just by the power generation from a BIPV system, which is about half of a rooftop solar system, the payback should be around 8-9 years.
Now that might be true for an existing building, but for one still on the drawing table, the financial viability would be analyzed by reducing the expected cost of a conventional glass facade.
As per my rough estimates, for the same coverage area, the replaced glass (depending of course on a lot of factors) could cost almost 30% to 50% of the solar modules used to replace them.
Solar panels account for about 60% of the solar system’s cost, so the savings on the glass cost alone could shave off at least 20% of the payback period. And don’t forget that larger systems are easier to finance.
To arrive at a complete picture, you would also look into the difference in installation costs, difference in operation & maintenance expenditure, savings from the HVAC load reduction, and savings from the electricity generated from the solar panels.
The Issue of Customization
There are usually two types of glass facade in buildings, view/vision glass (transparent) and spandrel glass (opaque). While progress is being made on ‘see through’ solar PV, for now it is easier (read: cost-effective) to replace spandrel glass as the PV modules do not have to be customized for passage of light. And are hence relatively cheaper.
As you know, a rooftop solar system can be installed at any stage, i.e. if the building is in planning, construction, or built stage.
For a BIPV system, however, the costs change radically when considering new projects vs existing buildings due to the duplication of several costs. Additionally, by working with the building developers at the planning stage, BIPV designers can suggest the optimum building orientation to maximize electricity generation from the integrated solar plant.
BIPV technology can be adapted to any building that requires a glass facade, including but not limited to skyscrapers, malls, apartments, modern homes, and more. U-Solar is working with apartment developers, mall owners, and other datacenters at the design phase to incorporate BIPV in existing as well as new projects.
Compared to the overall solar PV market, BIPV is still a niche solution.
However, newer technologies entering the market are already increasing the customization options, such as modules that have colored glass or wafers as well as modules that allow visible light to pass through. These can accelerate the adoption of BIPV systems by improving the building’s aesthetics.
Mr. Harinarayan shared that in order to enable the future growth of the BIPV market, “the key would be to open up larger demand by on-boarding more developers, and hence better economics across the sector.”
I for one think that the discussion on costs is a moot point. A lesson we repeatedly learn on technology costs is that it is simply dependent on scale! Given that building energy is a huge chunk of the demand pie, all we need to reason out is if BIPV is worth doing at large scale.
Credit for the images used in this post – U-Solar.