Balance of System (BOS) and energy yield improvement
Rationale for support
The focus of cost reduction and efficiency improvements for the past few decades has been on up- stream PV value chain segments, as PV modules have traditionally been the costliest component of a PV system. With the strong reduction of PV module prices, other parts of the value chain become more and more important for lower LCOE. Efforts should therefore be extended to other compo- nents apart from PV modules and other activities more focused on installation, operation, mainte- nance, decommissioning, etc. (the so-called “soft costs”). It is paramount that the PV sector pays more attention to the electrical energy yield of PV systems in real operating conditions (different climates, albedo, applications, mounting conditions, etc.). There are several factors that increase the overall electrical energy yield of PV systems, such as efficiency (objective 1) and the yearly electricity production (yearly kWh per kWp).
Since very high efficiencies are already achieved in power electronic devices, apart from reducing costs, main efforts must be focused on improving reliability, durability, longer lifetime and on offer- ing new functionalities related to the integration of PV. At the balance of system level, the highest priority must be given to the development of inverters, supporting structures (including trackers), electrical storage devices, energy management systems (EMS) and new component / solutions de- signs for specific applications (floating, AgriPV).
Inverters- power electronics
A recent review of the technology and market situation for the PV Ecodesign Preparatory Study (31) identified 3 main inverter categories.
String inverters used for a wide range of plant siz- es from a few kWs to large multi-MW installations. Their sizes can reach 200-300 kW. In principle, they are a better solution in plants with risk of mismatch- ing losses, provide more granularity in monitoring, improve the operation and maintenance through data analytics techniques and simplify the replace- ment and repair.
Module level power electronics (MLPE), mainly power optimisers (DC-DC converters) and micro-in- verters (DC-AC). The long-term durability of such devices is a critical factor as replacing defective components at module level could be expensive.
In terms of power conversion efficiency, central and string inverter products from leading manufacturers typically have an efficiency of 98 % and above, with module level devices slightly lower (95 %). Regarding circuit topology, single and three-phase inverters with and without trans- formers are current options and are used depending on the technical network.
Supporting structures have become an important part in PV systems cost breakdown, especially in large PV plants, in which tracking systems are used more and more often. In high radiation locations, 1-axis tracking structures of- fers lower LCOEs than fixed supporting structures, despite costing more. The latest product updates address the need to adapt structures to new applications (e.g. agrivoltaics). Larger and heavier modules lead to larger occupation of area and larger wind loads, increasing the weight and us- age of material. The lack of size standardization at module level makes tracker manufacturers adapt their products by creating a family of products suitable for different sizes and configurations (portrait, landscape, number of modules, different string configurations).
Energy Yield improvement
Concerning monitoring of PV energy production, current approaches use thermal sensors that are attached to the outside of PV modules and pyranometers or reference cells to evaluate irradiance at a given location. By replacing these with sensors laminated as part of the PV modules and/or integrated directly on the solar cells themselves, more reliable and properly distributed data would be achieved. This would help manufacturers monitor their systems’ performance. A large amount of data generated by sensors correctly distributed on the PV field would al- low the plant to be better modelled.
Targets, Type of Activity and TRL
By 2030, Balance of System components (electronic and structural) will be adapted to new PV module technologies and applications like bifacial technology. In countries with high PV penetration levels, solar PV will be inextricably linked to electricity storage, enabling investors and plant operators to maximise solar incomes and ensuring that so- lar energy is delivered when it needed or required.
PV modules will be selected and tuned for specific climates and applications. Novel characterisation and modelling tools will improve performance diagnostics and forecasting at cell, module, system and power plant level. PV systems will be equipped with intelligence in the form of electron- ics and sensors so that they can detect whether they are shaded or adapt their working current–voltage character- istics to temperature (see roadmap 7). The generated data from these sensors and electronics will build better models for array performance and for location- and application- adapted module design.
Finally, these intelligent and energy-yield optimised PV cells and modules will enable a faster integration of the various emerging PV applications in the urban environ- ment and in the energy system of the near future.
Develop integrated communication connection between inverters and other components (e.g. battery, PV modules, etc.) to automatically gather information (serial number, geolocalisation, etc.) of components and support the automatic creation of Digital Twins and PV Information Model.
Develop inverters with increased power density and reliability by introducing new wide bandgap semiconductors (GaN, SiC)
EPC and O&M -friendly design of inverters reducing typical failures found in the field (e.g. overheating). Introduce new features to enable semi-automatic field inspection techniques (e.g. Electrolumines- cence / Photoluminescence) through direct com- munication between inverters and drones or hand- held devices.
Develop inverters with the added features of grid forming and grid responsive requirements in sup- port of frequency control. Inverters’ behavior re- motely controllable to depending on the grid-sup- porting services required from the plant.
Mounting structures adapted to large PV modules by reducing the amount and nature of materials (especially those affected by international market prices
Control strategies for trackers to optimise produc- tion for complex terrain PV plants sites, considering bifacial technologies.
Optimised, lower-cost tracking systems. Tracking could be considered at an early stage in the design of specific modules suitable for the tracking setup.
Energy Yield improvement
To enable large-scale manufacturing of PV modules with embedded sensors, research is needed on the seamless integration of sensors in PV modules:
- integration within the module laminate of thin- film transistors (TFTs) to be used as thermal sen- sors and thin-film photodetectors (TFPs) to be used as optical sensors;
- integration within the module laminate of glass fibres (or other waveguides) with distributed Bragg reflectors to be used as temperature and strain sensors;
- integration of sensors directly on the solar cell, e.g. stress and temperature sensors
Use STC analysis for energy evaluation under realis- tic conditions for module design and cost analysis.
Develop passive (such as adding a heatsink to the rear side of the PV module, the use of phase change materials (PCM), and optical filters) or active cool- ing elements to keep the operating temperature low and uniform over the module area.
Develop reconfigurable PV modules that are shade-tolerant and can deal with dynamic changing illumination conditions.
Standardisation: the IEC 61853 Energy Rating series needs to be updated to include a procedure for bi- facial and multijunction climate specific energy rat- ing (CSER). Over time, this type of standard should complement STC from the early stages of laborato- ry development to analysis of the PV field in oper- ation.
Combination of degradation analysis and energy yield analysis. Module warranty to be linked to en- ergy produced under realistic conditions rather than an efficiency metric to increase energy production.
Including climate and environmental assessments/ site assessment/novel technology in PV system de- sign (what to build / where and how) through ad- vanced GIS technologies
Demonstrate that ICT technologies can contrib- ute to the security and safe operation of PV plants (blockchain for energy-money transactions in self-consumptions scenarios and energy commu- nities, cybersecurity in large PV plants, protecting energy trading AI agents, etc.)
Identify technologies/materials to be applied to existing PV plants to improve performance (e.g. anti-reflective/anti-scratch protective coatings on glass).
KPIs envisaged for this roadmap are:
|KPI||Target Value (2030)|
BOS components should contribute to the general objective of mak- ing PV the most competitive energy source and achieve a LCOE of 0.025 cEUR/kWh and 0,05 cEUR/kWh for IPV
BOS components should secure operational lifetimes of complete PV systems in the way of 50 years, similarly to PV modules or construc- tion materials
|Market and Production|
BOS should be available as the core element of PV integrated PV sys- tems, enabling the integration of PV everywhere: Low-cost adapted durable mounting structures, cabling and electrical components (e.g. PV connectors, DC switchgears, further safety components, etc.) for small or large PV system.