Building-Integrated photovoltaic technologies and systems for large-scale market deployment

BIPV technology market uptake has been hindered in the past years by the difficulties of the industry in providing holistic solutions complying with the key demands from decision makers and end-users. PVSITES has been conceived as an industrial joint approach to provide robust BIPV technology solutions to comply with these needs. The ultimate goal is to significantly enhance BIPV market deployment in the short and medium term.


The challenge of enhanced flexibility of design, outstanding aesthetical value and increased performance.

The solution: a wide portfolio of BIPV products based on crystalline silicon and CIGS photovoltaic technologies complying with market requests.

Every analysis on the current BIPV market situation shows that there are a series of demands from the stakeholders which have not been properly addressed by the BIPV industry. At module level, these key requirements are mainly related to the flexibility in design and aesthetics considerations, the demonstration of long-term reliability of the technology, compliance with legal regulations and cost effectiveness. The key stakeholders, and in particular architects and final clients are expecting BIPV materials to fulfil the following critical aspects:

  • A BIPV solution should be a PV active material but showing an appearance totally divergent to conventional PV modules (well-known for their poor aesthetical added value).

  • On the other hand, the final client/architect expects the same efficiency from BIPV as for conventional PV panels.

  • They expect from BIPV the same passive properties performance as non-PV products, in terms of mechanical properties, optical and thermal properties (light transmission, solar gain factors, thermal conductivity, external and internal reflectance etc.).

  • BIPV glazing solutions should be compatible with all well-known glazing treatment process as tempering, color frit-patterned, lamination process and rich encapsulation materials type compatible, and hard and soft surface coatings within other processes.

  • The decision maker (final client and architect) is expecting the BIPV solution to be compatible with a rich variety of shapes and formats including curve configuration.

  • No dimension constrains or at least the same ones as conventional materials are expected.

  • The decision maker demands from the BIPV provider that the product compiles any possible local building code and established standards.

  • Cost effectiveness: although some initial over-cost will be admitted, the net investment for selecting BIPV over other building material should never exceed a 20-30% of their initial budget. In other words, the BIPV must be close to materials parity at same passive properties performance level, and the main initial investment should be linked to the BoS.

  • Fully related to the later, the payback time should be competitive offering an attractive economic profitability. It should provide business models with payback times not larger than 5-7 years for the net investment.

In order to fulfill the aforementioned critical aspects, different technical approaches and actions will be taken within PVSITES. With a basis on crystalline silicon and CIGS photovoltaic technologies, a large portfolio of products will be generated, attending to former market demands. Glazed skylight and façade systems will include glass-glass back contact c-Si cell technology, XL format and large thickness BIPV modules, fully opaque façades with hidden busbars and L-interconnections and curved glazing with integrated flexible CIGS, all manufactured by Onyx Solar, with performances up to 160W/m2.

Flisom will demonstrate a portfolio of products based on a new lightweight, flexible, roll-to-roll monolithically connected CIGS solar modules on polymer films: solar roof tiles and façade elements with 10-14% module efficiency integrated on metal sheets using cost effective materials and processes; large area BIPV elements on metal sheets for integration in roofs and façades and bendable elements for flexible roofing.

Novel BIPV products V2_no_flisom_logo.pngAbove: Applications for flexible lightweight CIGS thin film solar modules developed by Flisom

 

Fostering synergies between multifunctional BIPV systems and other functional building elements.

The solution: Low concentration and passive solar control BIPV system.

Although space heating is still the dominant energy demand for buildings in most European countries, special attention should be paid to space cooling, since the energy consumption it accounts for (mostly electric energy) is growing rapidly as a consequence of global warming. Architectural integration of the BIPV systems proposed tackles this issue by fostering passive synergies with the thermal building envelope. Additionally, a low concentration photovoltaic solution with associated passive climate control for building integration in façades and skylights will be demonstrated in this project. Semitransparent glass-glass crystalline silicon PV modules in conjunction with integrated optical elements (Fresnel lenses) are proposed. The optical system, with no mechanical parts, is designed to concentrate solar radiation onto the cells during the central part of the year and allow light passing towards the interior of the building during the winter.

schematics.jpgLeft: Schematics of annual behavior of the low concentration system. Center: Winter behaviour, light into the building (up); summer behaviour, light onto cells (down). Right: technology demonstration in greenhouse, non-modular system.

An associated PV production enhancement and a reduction of the building cooling demand are expected during the spring-summer-autumn seasons. During this period, most part of the direct component of incoming solar radiation is redirected towards the solar cells, so that the PV modules behave as a low concentration system (approximately 7X), providing up to 20% annual over generation for high irradiation climates, up to 13% for lower irradiation levels (calculations performed with Design Builder software, with an in-house method to simulate the effect of the lenses). At the same time, as there is a decrease in direct solar radiation within the building, greenhouse effect and its related building overheating are reduced. During the winter, diffuse radiation and most direct radiation reach the internal part of the building, not penalizing heating demands, and the PV system produces under non-concentrated light, as a usual PV system would.

This technology has been previously demonstrated by Tecnalia in the greenhouses sector. In this project, it is proposed to introduce this technology into the building environment by demonstrating an integrated system which will eliminate shading losses, enhance system durability and reduce manufacturing and installation costs. In the case of skylights, the whole system will be implemented as a modular curtain wall. A ventilated façade implementation is also considered, keeping the Fresnel lenses perpendicular to the glass pane. In this way, the optical design of the lenses is analogous to the skylight configuration. Moreover, aesthetics and users visual comfort are unaffected. Sunscreen slats are also foreseen.

 

The need for a software tool for the joint simulation of BIPV products and building energy performance.

The solution: An accurate, user-friendly, integrated software tool for performance prediction of BIPV (and also building adapted) products and their impact on building energy performance will be developed.

The development of a software tool for the prediction of BIPV products and building energy performance is an answer to a series of well-defined customer needs:

  • Specific design tool for building-integrated photovoltaics products: simulation tools currently available do not focus on BIPV, and do not take into account the building related aspects of the PV installation design process.

  • Libraries of standardised BIPV products: designers may not be PV experts and need access to a wide range of pre-designed BIPV products with well-established properties.  On the other hand, this is a powerful marketing strategy for BIPV manufacturers.

  • Compliance of BIPV products with legal requirements: a major concern for designers is the compliance of the project with legal requirements when innovative products are introduced.

  • Establishing bridges between architects – engineers – PV manufacturers:  BIPV projects often lack proper collaboration between the different parties involved.

The tool developed within this project will be unique in the market, offering an integrated PV-building approach, providing updated information on legislation compliance, and setting a simplified framework for architects and thermal engineers to share information on the building project from different levels of software complexity, adapted to their needs. All along this work chain, PV, BIPV and construction products manufacturers are also involved through product libraries containing all the technical information needed for the design process.

 

The need for a solar BIPV generation more predictable, manageable, grid-friendly and profitable in terms of building energy savings.

The solution: A combination of flexible and high efficiency grid interface for BIPV systems and new building energy management strategies will be developed.

The main drawback of PV energy is its dependence on variable solar resource impacting on grid operation. Potential countermeasures are well-known: improvement of solar PV energy short-term forecast, demand response methods and utilization of energy storage. However, these techniques mean significant external costs reducing PV competitiveness and, consequently, they are still far from being worthwhile.

The integral solution developed within this project, combining flexible and high efficiency grid interface and new building energy management strategies, will overcome this inconvenience through:

  • Improvement on short-term solar BIPV forecast by means of the development of low-cost and reliable BIPV generation and building electrical demand 24-hours-ahead forecasting tools based on regressive and learning-machine algorithms.

  • Increase of BIPV generation excess value by means of peak-shaving and maximizing self-consumption rate at the most profitable time, taking advantage of predicted daily evolution of BIPV generation and building electrical demand.

  • Reduction of storage system costs in terms of cost per energy unit served by means of a practical selection and sizing of electrical storage system for each use case.

  • Reduction of required storage capacity by means of characterization of flexibility potential of different end uses and integration of active load management tools in building energy management system.

  • Reduction of cost and increase of efficiency, flexibility and robustness of power conversion systems by means of the development of two new design solutions (a low-cost and high efficiency PV inverter with DC coupled storage system and a low-cost and robust PV inverter based in SiC technology) and the selection of the most suitable alternative for the integration of the electrical storage system.

 

The need to demonstrate reliability of advanced BIPV solutions by effective incorporation onto real buildings

The solution: high impact demonstrations in real buildings and experimental facilities throughout Europe.

The progressive acceptance of BIPV installations require advanced showrooms with a high visibility towards involved stakeholders and the general public. Advanced training activities should be offered to foster the integration of BIPV in building works. In PVSITES, the proposed module, grid interface and energy management technologies will be demonstrated in 6 real buildings covering different EU electricity markets and climates, building uses (residential, industrial, commercial), new buildings and retrofitting, public and private property, different architectural implementations provide the largest potential for replication.