Technology update: How to cut cost even further

This article is the fourth entry in SolarPower Europe’s 10-part blog series on ‘What’s Hot in Solar’.
“Solar has become the lowest-cost power technology in many regions and still has a lot of leeway to cut cost,” write Michael Schmela, Executive Advisor and Aurélie Beauvais, Policy Director at SolarPower Europe

Now that solar has become the lowest-cost power technology in many regions, there have been few voices asking if there’s still further reduction potential. The answer is a clear yes! Solar still has a lot of leeway to cut cost – and there are many ways to tap into this potential. Naturally, the solar module and its process materials as the biggest contributor to system cost are the prime focus for cost reduction efforts. At the same time, all other parties involved in production of hardware and generation of power are working hard on solar’s competitiveness to improve even further. SolarPower Europe has looked at the latest developments in different technologies to reduce solar system cost and at intelligent applications that offer synergies between solar and other applications.

Mono – further growth insight: Depending on the source, monocrystalline silicon was at parity or had already taken over the leadership position from multicrystalline silicon in 2018. In any case, the scale will swing further towards mono this year and beyond, as all silicon ingot crystallisation capacity expansions are focussing on the mono variant, which has less defects than multi, enabling production of higher cell efficiencies. In April, LONGi Group announced that it will expand its mono ingot/wafer output from 28 GW in 2018 to 65 GW by 2023 (that’s nearly two-thirds of global installations in 2018). Cost improvements in mono wafering/crystallisation technology had pushed the development from multi to mono, while a pull has been coming from higher efficient mono PERC cell technology.

PERC – for everyone: What mono now means for wafers; PERC does for cells – it has become the new standard technology. As Passivated Emitter Rear Contact (PERC) solar cell technology brings 0.5-1% points efficiency improvements with little more cost for additional production equipment, the bulk of crystalline silicon cell equipment investment is mostly being spent on PERC tools these days. Now the big question is: what comes next?

Beyond PERC – Passivated Contacts or HJT? The next evolutionary step in solar cell technology following PERC are likely Passivated Contact cells, often called TOPCon, where a sophisticated passivation scheme is adapted to advance cell architectures with the promise of even higher efficiencies. In January 2019, JinkoSolar announced a 24.2% world record efficiency TOPCon cell based on n-type monocrystalline silicon substrate. So far, only very few companies are producing commercial quantities of TOPCon cells, but there is a lot of interest.

An even higher efficiency potential is offered by Heterojunction technology (HJT), which holds the overall cell record for silicon solar cells at 26%. While Sanyo/Panasonic have been producing HJT modules exclusively for many years, the expiry of key patents has given others access to the technology that combines the best of the silicon wafer and thin-film worlds. A number of equipment providers now offer HJT processing tools, and the first new commercial cell/module lines have been in pilot production and/or ramp-up by ENEL Green Power and a few others. While HJT has several advantages over traditional crystalline solar cells, showing a leading low temperature coefficient, the highest bifaciality of all cell technologies and much less production steps, it requires investment in a completely new line.

Bifacial – back & front: The technology that will help bring down LCOEs of solar power plants the most in the short run are bifacial solar modules that generate power not only on the front side but also on the back side. This results in power gains between 5 and 30%, depending on solar cell technology used, location and system design. With today’s new high-efficiency cell generations all being ‘naturally’ bifacial and issues with standardisation or bankability mostly solved, the technology is rapidly gaining market share – from 10% in 2018, to 30% in 2021, according to the International Roadmap for Photovoltaic 2019 (ITRPV).

Half cells – easy power gain: When most people think about a solar cell, they see a blue square slice of silicon. In the future that might be different. Using half cells is a simple but very effective means to increase module power. By cutting a fully processed cell into two parts, resistance losses can be reduced, providing a power boost of about 5 to 6 W on the module level. Basically, every module manufacturer now has half-cell products in its portfolio – and will raise shares as clients get used to the new solar look.

Multi-busbars: One of the easiest ways to reduce resistance losses of solar cells is to add more busbars. While using 3-busbar cells was the standard in module assembly only a few years ago, the industry successfully shifted to 4-BB cells in 2017. Today, basically everyone has upgraded its latest standard product range to 5-BB design. The next step is so-called multi-busbars (MBB). Here, over a dozen wires are used, that are so close to each other that the finger width can be reduced significantly. On top, MBB enables eliminating the busbars from the cell layout. This helps in saving silver paste consumption by up to 80% on the cell level.

The 400 W+ module: Improvements in cell technology and module design – such us multi-busbars, half cells, shingles, all of which can be generally combined – and the use of somewhat larger wafers can help raise the power rating bar of a crystalline solar module above the 400 W level for a panel with 72 cells (or 144 half-cells). Higher power ratings mean fewer modules and less space requirements for solar plants of any size, which reduces installation, system material and land costs.

Double glass or glass-backsheet: Glass-glass modules have been around for many years, but until recently, their share was, for a number of reasons such as heavy weight, negligibly small compared to glass-backsheet modules. Even 30-power performance warranties, that are five years longer than the typical warranty for a glass-backsheet module, didn’t help too much. This has changed with the advent of bifacial modules, which need transparent back covers to generate power on the rear side. A highly transparent glass cover seems to be the natural fit, and module manufacturers have been using almost exclusively glass-glass for their bifacial products so far. However, in the last few months, a number of backsheet suppliers came out with new transparent products, and the first module manufacturers have started offering bifacial glass-backsheet solar panels with 30-year power warranties as well. Glass-backsheet module technology is now ready for the bifacial era as well.

Thin & large: Thin-film technology has made a strong leap with the introduction of First Solar’s Series 6 CdTe technology. The Series 6 modules come with a much larger form factor of 420W+, a superior temperature coefficient, better spectral response, a true tracking advantage as shading has less impact on thin-film modules, and reduced soiling, which results in high energy yields and low LCOEs.

Big, small and very small: The importance of the inverter’s role in PV systems has only been increasing with the arrival of digitalisation in solar. Primarily used in the past as a means to convert DC into AC power, today, inverters are the real brains of solar systems – they cope with all types of storage systems, are a key tool for efficient solar power plant operation & management, also regarding grid services, and a partner of intelligent energy management systems in homes or the solar mobility world. Regarding size, on the one hand inverters are getting bigger, with central inverters now available over 5 MW to address the needs of ultra-large utility-scale plants. On the other hand, there is the popular concept of commercial-size inverters with power optimisers to more efficiently operate a solar system, which has found new proponents, while module-integrated micro-inverters are also seeing increased traction as bifacial modules and a growing rooftop market with a focus on safety provide the grounds for the stronger growth of module-level power electronics.

Following the sun: Today’s large utility-scale solar power plants are all using tracking systems that have basically become a standard for utility-scale PV plants in southern regions. They operate reliably, and the little higher investment over fixed mounting systems is more than compensated by lower LCOEs. The latest product updates address the needs of bifacial modules to have open access to the grounds to be able to generate power on their back side.

Solar & Storage – a dream team: Stationary battery storage is quickly gaining in popularity in an increasing number of solar markets, in particular in established residential PV rooftop markets, where the technology already supports the dissemination of solar-self consumption systems, and soon will be crucial to bring solar penetration to the next level. In Germany, Europe’s largest solar storage market, 45,000 residential storage systems were installed in 2018, up 20% from 37,500 in 2017, according to EuPD Research. In certain regions, more than every second solar system is already sold with a storage system.

Floating Solar – sun and sea: Water bodies can be great locations for solar power plants. The water keeps the PV modules cool, which has a positive effect on power yields, while in return, the solar panels can protect the surface of drinking water reservoirs from air pollutants or evaporation. In addition, this solar application often avoids competition on space usage. While still very small, there is huge interest in floating PV, in particular in Asia. At the end of 2014, only 10 MW was installed, increasing to 1.1 GW by September 2018. Just recently, a new floating system with 150 MW was installed, which is now the world’s largest. According to the World Bank, if only 1% of all available area were used, the world could install over 400 GW of floating solar systems.

Agri PV – Sun farming and more: Solar can be a great fit with agriculture – a sector often considered a competitor on available space. It doesn’t have to be that way. You can install solar in such a way that agriculture and animal farming is not negatively impacted. In fact, highly innovative Agri PV business models support the sustainable electrification of agricultural processes and deliver symbiotic business models to bring farming to another level. Agri PV can help in solving the political dilemma of appropriate land use; it can also help in improving the production yield for both power and crops. Moreover, it provides local farmers with additional income. The potential of Agri PV is huge because of its ability to adapt to any geography: for example, in very dry areas, Agri PV can help retain humidity for crops and create micro-ecosystems supporting food supply in the world’s most arid regions.

Solar meets coal – PV for coal regions in transition: Solar is now increasingly used to support the restructuring of depressed regions, such as former coal regions. After a coal mine stops working, a key question is what to do with this brownfield area. One possibility is to transform former coal mines into solar farms, a trend that is expected to grow as the world progressively transitions to a fossil-free energy system. A recent study from the EU Joint Research Centre found solar to be particularly suitable for employing former coal workers and to help drive regional development.

For more solar trends, download the Global Market Outlook for Solar Power 2019-2023

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