BIPV is a promising new technology in the field of solar industry. More and more solar power plants around the world are used in close association with the architectural design, organically blended into the urban environment.
BIPV systems: features and prospective applications
One of the most promising renewable energy technologies is photovoltaics. Photovoltaics (PV) is a truly elegant means of producing electricity on site, directly from the sun, without concern for energy supply or environmental harm. These solid-state devices simply make electricity out of sunlight, silently with no maintenance, no pollution, and no depletion of materials.
There is a growing consensus that distributed photovoltaic systems that provide electricity at the point of use will be the first to reach widespread commercialization. Chief among these distributed applications are PV power systems for individual buildings.
Interest in the building integration of photovoltaics, where the PV elements actually become an integral part of the building, often serving as the exterior weather skin, is growing worldwide. PV specialists and innovative designers in Europe, Japan, and the U.S. are now exploring creative ways of incorporating solar electricity into their work. A whole new vernacular of Solar Electric Architecture is beginning to emerge.
According to SEIA (Solar Energy Industries Association) report the maximal growth of installations of photo-electric stations in the segment of private home solar power-stations during last few years. On the average total power capacity of solar power station was increasing about 50-60% annually during 2014-2016. Overwhelming majority of houses that use energy of the Sun, generates electricity through stationary roof solar power-stations. Thus, together with market growth, two basic tendencies are clearly noticed:
- Technological factor: increase of efficiency of private solar power-stations, growth of their power capacity, and also creation of systems that will be able to provide functioning of households in fully autonomous mode due to installation of high-capacity storage systems and optimized processes of accumulation/consumption of electric power.
- Aesthetic factor: house owners want photo-electric modules to fit completely naturally into architectural solutions of their houses, to correspond with main style of a house internal decorations.
Manufacturers, trying to satisfy all requests, offer package solutions to their consumer; more and more popularity belongs to solar power-stations integrated (built-in) into buildings, or BIPV solutions (from Building Integrated Photovoltaics).
Features of BIPV systems’ development
A Building Integrated Photovoltaics (BIPV) system consists of integrating photovoltaics modules into the building envelope, such as the roof or the facade. By simultaneously serving as building envelope material and power generator, BIPV systems can provide savings in materials and electricity costs, reduce use of fossil fuels and emission of ozone depleting gases, and add architectural interest to the building.
BIPV are photo-electric modules, that are intended not only for electricity generation but also are the valuable part of a house as wall material or roofing coverage; they can be used as covers, peaks and other architectural construction elements. It is thus necessary to distinguish two concepts:
- BAPV (Building Attached PhotoVoltaics) are photo-electric modules that can be considered as additional structures of a house. They are assembled, when erection of a building is already complete, they perform the basic and only duty of electric power generation by transformation of solar radiation. They can be dismantled at any moment, integrity and building reliability will not suffer here. Simplest and most widespread example of BAPV are roof solar power-stations that are assembled over main roof coverage.
- BIPV (Building-Integrated PhotoVoltaics): solar modules are integrated into a building, they perform the same functions of those elements, into which place panels are built-in; BIPV-elements protect a house from moisture, wind, improve thermal and acoustic proofing, simultaneously working as solar panels, namely generating electric power. Their installation is planned on the stage of building design, their dismantling is possible only on condition of substituting them by equivalent building materials.
Experiments with BIPV started in 1970s, when this term actually appeared. Photocells, reinforced by aluminium alloy, were for the first time built in roofs and cornices of a building. Imperfection of technologies of the time, foremost in production of photo-electric modules, made such solution ineffective enough. Experiments proceeded in future, using different technological and architectural solutions, but only few years ago this small and poorly developed niche began to form into separate market segment of solar energy industry.
Such development is connected foremost with development and enhancement of thin-film flexible solar modules technology. Exactly these modules, in opinion of specialists, will begin to play the main role at BIPV market, because except higher productivity as compared to monocrystal and polycrystal panels thin-film modules have variable degree of transparency, and also can be produced in different colour options. It gives the opportunity to designers to extend traditional architecture designs and harmoniously include hi-tech elements into traditional architectural styles, converting a house into esthetically attractive energy-generating structure.
According to estimations of United States Department of Energy (DOE), in a long-term prospect BIPV systems can provide up to 50% of electric power necessities of the United States. Demand on BIPV systems constantly increases against the background of permanent decline of photo-electric modules prices, and the issue is not only about creation of energy-generating system.
Consumers are interested to get the integral system that will be able to provide maximal energy independence of an object. The market of BIPV already attained some point when it is ready to swift development. But some critically important questions must be decided before such development.
Technical and building standards
New BIPV products, that imitate original appearance of traditional construction materials while performing their energy-generating functions, are considered as single integrated material that must have own standards. From one side, these materials must meet building requirements (in other words structural and mechanical parameters), and from other side they must to meet electrical engineering standards, developed by International Electrotechnical Commission (IEC).
New European standard EN 50583, that determines parameters of BIPV, could be named as large step towards progressive development of the industry.
Fist of all, exact and unambigiuous definitions of BIPV are given in this standard. Integrated photo-electric panels will be considered as BIPV only on following condition: after extraction from building these panels must be substituted by other building materials or constructions to avoid violation of building integrity. The key feature of EN 50583 standard lies exactly herein, it gives clear definitions and outlines BIPV parameters, actually giving them equal rights with traditional building materials.
In addition, functions that can be performed by solar power-stations (photo-electric modules) as part of building construction are clearly defined by the standard:
- Providing of mechanical resistability and structural integrity of a building
- Protecting from aggressive weather factors: snow, rain, hail, wind.
- Providing of power saving: thermal insulation, luminosity level, shading.
- Increase of fire resistance.
- Observance of acoustic isolation norms and standarts.
- Using as a delimiter between internal and external apartments.
Problems of planning and building
Problems of planning of BIPV houses can be divided into two groups:
- Optimization of photo-electric modules location with the purpose to receive maximal amounts of electric power generation. Modern software allows to perform calculations on possible generation amounts to a high precision, and also to obtain maximal amounts due to correct selection of element basis of solar power-station and location of solar modules.
- Development of architectural and construction design of houses with BIPV. Nowadays projects with BIPV systems are not very popular, most architectural offices have a minimum level of experience in building designs with BIPV technologies. However, acceptance of single standard have already considerably simplified designers’ work, they can now operate with well-known concepts and definitions.
Installation of BIPV systems is relatively new direction, therefore it will demand builders’ training to level up their skills. Rentechno company is ready to provide professional education, consultations and services both on planning stage of a residential house or an office building, as well as directly during building and installation works. Our specialists will provide correct (from architectural point of view) installation of BIPV systems and their specialized connection both to electrical system of a house and to general electric system.
Most perspective areas to use BIPV technologies
Many proprietors of private houses, interested in transfer to renewable sources of energy, were forced to give up their desires because of insufficient aesthetic attractiveness and bulkyness of ordinary solar panels. Using of BIPV solar pamels as functional building materials opens new possibilities for architectural solutions.
Today it is one of mostly discussed, but yet not widespread solutions, when cement or clay tiles on building roof are substituted by observationally equivalent-looking photo-electric modules.
In October 2016 head of Tesla Motors company Elon Musk announced “solar roof”: photo-electric modules, that can replace ordinary tile or metallized tile. It is declared that “solar tile” will be presented at the market in four options: ground glass, slate, tuscan and texturized. Tiles will be manufactured from quartz glass, therefore their reliability and durability will be 2-3 times better than concrete, clay or metallic counteritems. Thus their efficiency will make 98% as compared to ordinary solar panels. Electric tiles are able to pass solar radiation through, but they look opaque, if you look at it not at right angles.
For this very reason solar panels made as tiles are visually indistinguishable from an ordinary usual roof, what makes their advantage compared to modern roof solar power-stations. Musk announced, that prices on “solar tile” in course of time would become comparable with traditional roofing coverage. The very first samples must appear at the market already in summer 2017.
Sizes of photovoltaic panel tile are little bit more than standard tile, this allows to minimize electric connections and improve general reliability of the electrical system. The circumstance that weight of photo-electric modules is less than concrete or clay tile, also works to the advantage of photovoltaic tile, and allows to perform roof construction easier, bringing down requirements to bearing strength of walls and foundation. All this results in cost cutouts on construction of a house.
Roll roofing coverages
One of the most popular building materials for roofing coverages is presented as different options of bitumen-based roll coverages, also called soft tile.
Now producers are ready to offer equivalent thin-film laminate that combines properties of bitumine coverage and solar battery. These long stripes have basic advantage of minimal quantity of electric connections. Additional benefit is that their installation almost repeats similar processes for traditional bitumine roofing coverages, that opens large horizons before roll-type photo-electric elements in terms of installation in case when repair or replacement of roofing material is needed.
Lately there is strong interest among modern architects to solar batteries use as facade panels, that allows to create innovative, esthetically attractive building facades.
Perspective of this direction is determined by two factors. First of all, installation of solar panels on the walls of residential houses was actively used in BАPV systems. Second factor is that prime price of facade panels is just a little higher, than BIPV panels, therefore it will not result in substantial expenses growth in the process of building construction.
It is one of very actively developed directions, and in fact one of the most perspective markets. According to researches, commercial buildings consume about 40% of all electric power in the USA and building proprietors are interested to cut off their bills for electricity. According to forecasts, mounting of “solar” windows will cover up to 30-50% of a sky-scraper electric energy necessities; further technological improvements will raise this share even more.
“Solar” windows are installed as transparent thin-film solar batteries that are just sticked over glass in the simplest model. The basic problem of such construction lies in following controversy: useful work of a solar battery is based on absorption and transformation of solar energy. The more solar energy a battery takes in, the less sunlight will get into a room. Actually, part of solar energy, regenerated into electricity, should be used again to achieve acceptable levels of internal luminosity, especially during morning and evening hours. On the other hand, during daylight time/summer months this partial shading may play quite positive effect, reducing thermal load on an apartment and allowing to bring down energy consumption on apartment conditioning.
The main problem is low productivity of transparent thin-film solar batteries, that now maximally makes about 7%, substantially losing to traditional solar batteries, made from crystalline silicon. Alternative “solar windows”, where photo-electric elements directly become part of glass itself, are now under active development.
For today most effective price/quality ratio among BIPV solutions belongs to systems, built on the basis of glass/glass silicic crystalline modules. They combine cheapness of traditional solar panels and aesthetic pleasure of thin film modules. Exactly glass/glass panels will be most demanded product at the market in the nearest 2-3 years.
Foremost, glass/glass modules are able to maintain very large loads about 8000 Ра. For comparison, such pressure on roof of a house is created by 8 m thick snow layer. By this parameter glass/glass modules are 1,5 times more effective than standard solar panels. Other advantages should also be mentioned:
- Use of special frame allows maximal simplification of installation process for solar modules. A fitter can set up to 4 panels in just 10 minutes after short instruction briefing.
- Standard solar panels start to lose generation amounts when temperature rises. Glass/glass modules are less rerceptive to thermal influence, at identical temperature values they generate 10% electricity more than standard panels.
- When installing “glass/glass” modules, there is no necessity in additional preparation of a roof or in making load carrying structures more durable. For example, during capital roof repair it is enough simply to take off old roofing coverage and set “glass/glass” solar modules into its place. Actually, installation of “glass/glass” modules saves cost of roofing coverage to a house proprietor due to multifunctionness of BIPV panels.