Saturday read: Keys to urban solar

From pv magazine 09/2021

Humans spend much of their time inside. Buildings are key to our daily lives and significantly impact our health and well-being. Most also have substantial carbon footprints, employing heavy use of fossil fuels from their construction, through use and demolition phases.

According to Project Drawdown, a nonprofit organisation established in 2013 under a collaborative effort involving 200 researchers and advisers to model solutions to reverse global warming, 230 billion square meters of building space exists worldwide and another 65 million could be added this decade. Currently, it says, buildings account for 32% of energy use and 19% of energy-related greenhouse gases in the form of heating, cooling, lighting, appliances, and machinery.

Energy efficiency

While innovative green plans are being formulated for new builds, there are significant gains to be reaped from retrofitting existing buildings, particularly as many of those standing today will still be in use in 2050, according to the International Energy Agency (IEA).

It adds that in 2019, almost two-thirds of countries lacked mandatory building energy codes. To be in line with the Sustainable Development Goals by 2030, it says all countries must adopt such codes. In addition to “high-performance” construction, it believes energy-efficiency renovations of existing buildings must double from 15% to at least 30% to 50%.

“Improving building energy efficiency is one of the most cost-effective and fastest ways to reduce electricity demand and associated fuel imports, while indirectly slashing carbon emissions as well as improving local air quality and public health,” says Project Drawdown. It believes enhancing energy efficiency, shifting energy sources, and addressing refrigerants are key to transitioning buildings from being carbon-intensive to potentially net-positive.

In this sense, solar and energy storage have a fundamental role to play, particularly when it comes to cooling and heating and, due to their increasingly small costs, for low-income households struggling with high energy bills.

Obvious choice

Representing an annual increase of 46%, 60.6 GW of residential and commercial and industrial (C&I) solar PV rooftop systems were deployed globally in 2020, reports SolarPower Europe (SPE) in its Global Market Outlook for Solar 2021-2025. Looking ahead, SPE predicts these figures will grow to nearly 96 GW in 2025.

This sector is perhaps the most obvious way to help green buildings; and with the right conditions, it can evolve very quickly. As SPE notes, “Vietnam is a very encouraging example, showing that the solar industry is now ready to develop even more sophisticated market segments like rooftop PV from basically zero to world record levels in a very short time – all it needs is the right policy and technical framework conditions, and a workforce with the right skillset.”

Already, steps are being taken to improve the policy landscape. For example, last year, the U.S. state of California introduced a new law, which made solar a mandatory part of new-build homes, while in some German states like Berlin, it is now compulsory to install rooftop PV on all new and renovated buildings.

Solar solutions

SPE adds that with the evolution of residential and commercial power consumers into prosumers, PV panels will also positively contribute to building materials. Still a niche industry, building integrated photovoltaics (BIPV) has inventive solutions, like solar facades, tiles, and windows, which can improve energy efficiency. However, the technology is relatively nascent, and the industry faces many hurdles, like certification and approval processes, as pv magazine reported in the July edition (pp. 34-35).

The PV and energy storage industries, along with digitalisation and electric vehicles, will also play a strategic role in the development of such things as district heating, energy communities, smart cities, and microgrids. Innovation will be key to driving such initiatives.

Australian company eleXsys Microgrid Technology, for example, has designed a platform that enables a “massive increase” in the amount of renewable energy on local electricity grids by eliminating export curtailment and facilitating a two-way flow of electricity (pp. 86-89).

The product is described as an advanced grid-forming, power electronics Internet of Things device, integrating a suite of artificial intelligence software applications, which can increase the size of grid-connected C&I microgrids up to 10 times. It is currently working with Ikea in South Australia to combine commercial-scale solar PV and batteries with its energy management system to provide up to 100% of the Ikea store’s energy requirements. EleXsys aims to deploy 1,000 similar microgrid sites across Australia and has identified business opportunities in France, the United Kingdom, Ireland, the United Arab Emirates, and the Asia-Pacific region.

The U.S. city of Ithaca, New York, meanwhile, plans to eliminate or offset all its carbon emissions by 2030 by retrofitting existing buildings with electric heating, solar PV, and battery storage, and greening the electricity grid, reported The Guardian in August. It is exploring private equity to help building owners decarbonise. The goal is to create 1,000 new jobs and redirect 50% of the financial benefits of the city’s Green New Deal plan to low-income residents.

Pump it up

The heating and cooling of buildings is another area where solar and energy storage can reduce emissions. Project Drawdown says of the around 32% global energy generation the global building sector uses, more than one-third goes to heating and cooling. It adds that at the end of 2015, an estimated 1,350 solar thermal cooling systems had been installed worldwide, with Europe comprising around 80% of the market.

The IEA calculates that cooling energy use in buildings has doubled since 2000, “making it the fastest growing end-use in buildings.” It estimates that by 2050, around two-thirds of the world’s households could have an air conditioner (AC). “China, India and Indonesia will together account for half of the total number,” the IEA says.

Solar cooling can include the direct use of PV with a heat pump or AC, or solar thermal collectors that use a thermally driven cooling device such as a sorption chiller, says the IEA. Heat pumps are an interesting solution because they can easily replace gas fired heating. To be effective, they must be able to reach high temperatures of up to 75 degrees; however, currently the higher the temperature, the lower the efficiency. Technological progress is being made, though.

For example, this August, Norwegian independent research organization Sintef, Norwegian compressor manufacturer Tocircle, and the Norwegian University of Science and Technology announced a high-temperature industrial heat pump than can work with pure water and reach a temperature of up to 180 C.

PV in the city

In the fourth quarter of 2021, pv magazine’s UP Initiative will discuss the role solar and energy storage can play in greening the world’s urban spaces. We will investigate the technologies in the BIPV and heat pump industries, examine supporting policies and initiatives emerging worldwide, and look to those markets, like Scandinavia, which have successfully built district heating systems, to see if their knowledge can be transferred.

We will also feature innovative projects that are attempting to change the urban status quo and, ultimately, seek to answer how a step change can be made in the overall electrical grid system supporting buildings and their inhabitants. Because to achieve real change, we cannot just focus on the individual level, but must understand how all these buildings tie into the wider system. As the saying goes, united we stand, divided we fall. If you want to contribute, contact ­up@pv-magazine.com.