Solar photovoltaic panels are a proven and mature technology that has diffused successfully into green architecture; the use of solar panels in buildings constitutes a solution towards green energy, in line with contemporary architectural design and with economic and environmental viability.Solar photovoltaic (PV) panels have seen a huge development in recent past years. Today they constitute an ideal solution for green buildings (see Zero energy buildings) and can be mounted almost onto any type of building ranging from contemporary modern designs to more traditional buildings. Their use ranges from substituting various building elements and materials, such as glass windows or glass walls, to complementing existing structural materials in various building solutions, such as providing for building shades. Solar panels’ ability to produce green energy from sun power makes them a key diver and an important tool towards combating our environmental challenges. Incorporating Photovoltaic technology in architectural design improves the environmental behaviour of a building without influencing the comfort, aesthetics or cost of the building.
Solar panels as structural building elements
With the term building-incorporated-solar panels, we refer to the incorporation of solar panel technology as a primary structural element of a building. Thus, building incorporated solar panels are solar panels that have been included within the architectural design of the building and they constitute a main aspect of the building shell-structure. Consequently, they are installed during the construction phase. For example, incorporating a photovoltaic wall on a building does not mean adding photovoltaic panels on to a building wall but, constructing the building wall itself out of photovoltaic panels. In this way, building-incorporated solar panels are both a structural element of the building and a solar system for the production of green electricity, leading to savings for both building and energy costs.
Types of Photovoltaic (PV) panels and their selection criteria
PV panels based on their degree of being incorporated
1. Typical photovoltaic panels are PV panels framed with glass and plates. This is the most popular PV type that is typically used on building roofs or in large photovoltaic installations in remote areas.
2. Semi-transparent glass photovoltaic frames (double glazed PV-crystalic frames). These PV frames are suitable for use as building-incorporated solar systems with thermal insulation properties; consequently they can be used in place of double glazed glass structures in building facades.
PV panels based on construction materials.
The main categories of photovoltaic materials are:
1. Crystalline silicon (monocrystallic or poly-crystallic) are the most popular systems used in photovoltaic applications (normally referred to as solar panels) with performance efficiencies between 11%-16% and minimum surface area per kilowatt of capacity installed ranging at 7-10 sq.meters.
2. Thin film solar technology incorporates thin films of photovoltaic layers on to a thin base that can be made of stainless steel, glass or composite material. Thin film PV panels are less efficient than crystalline silicon PV panels but they cost less. As their name suggests, they are very thin making their application highly flexible and can be installed almost on any surface.
PV selection criteria; Solar Panels Performance and Solar Panels Cost
The performance output of photovoltaic panels is based on their annual energy production in kilo-watt-hrs (kWh) and their production cost. However, these figures may vary depending on the location of the installation. A solar photovoltaic system in California (or in any location with similar environment) at optimum inclination and optimum orientation to the South may produce around 1300 to 1500 kWh/kWp in a year. The output performance of photovoltaic panels is influenced by many factors such as the climatic conditions of the site location, the geographical latitude of the site, inclination and orientation of PV panels, and PV panels’ age; typical solar panel manufacturers guarantee their PV efficiency to be above 90% for the first 10 years and above 80% for the next 10 years. The cost of solar panels, according to 2013 prices, ranges between “$1750 – $2500 per Kw of installed capacity (average Solar panel cost per kw)” though solar panels cost ranges depending amongst other factors on the manufacturer brand, installation site, and installation size – more on financial assessment of solar panels on how much solar panels cost)
Incorporating solar panels in buildings
The technological advancement in Photovoltaic systems has made it possible to maximize the benefits from using PV panels in the building sector; not only through maximizing the output performance of Photovoltaic panels but also through extending their capabilities of being incorporated as flexible structural building elements. Advanced PV panel solutions can be incorporated on a wide range of applications and on different types of buildings, ranging from tall high-tech buildings with demanding design features to traditional old buildings with severe design restrictions (e.g. buildings of architectural heritage, or imposed town planning restrictions). Solar panels may be incorporated on different aspects of a building; typical applications may include, building roof tops (flat roof mounting or at south inclined roof-tops), building facades, solar blinds and shading structures and skylight solutions for natural lighting.
Photovoltaic PV panels on roof tops
Photovoltaic PV panels on building facades
Photovoltaic panels can be incorporated in the building materials within the building facade.
These types of PV panels come in different shapes and colors to match the architectural and design features of a building. Their wide variety and design flexibility allows their use on a wide range of architectural and green building applications. They can me mounted on external building walls providing for a shading solutions, or insulation solution or adding to the aesthetic effect of the building while operating as an energy producing photovoltaic system. Apart from external walls, PV panels can also be installed on semipermeable facades. Under this mode, they are placed in place of conventional glazing solutions. Their installation method may vary from being installed onto an existing face or be a complete supplement of conventional double-glazed frames; due to their modular structure, they can be a perfect substitute for conventional glass facades. Of course, their size, color and transparency may vary to match different needs.
Photovoltaic PV panels on shading structures and sky lighters
Using Photovoltaic panels in shading structures in buildings has two basic advantages:
1. Cost savings from conventional shading structures (solar blinds); Semitransparent PV panels provide adequate internal shading and they come in a range of solutions with respect to their degree of transparency.
2. While saving energy from shading, they produce green electrical energy that can be used either as a power source for the building (partial source) or as an investment via FITs (i.e. selling electricity on the power grid).
A remarkable fact is that inclination of the Solar PV panels for optimum solar shade coincides with the inclination φor maximizing solar electricity; thus their incorporation to building facades and shading structures can be highly beneficial.
Other PV panel installations
Similar applications to the ones outlined for incorporating solar PV panels in buildings include their installation on to remote shading structures (e.g. in parking places) or as shading panels and as protective noise barriers in highways near residential areas.
Building-incorporated solar PV panels vs. conventional structural materials
The assessment of the benefits of using Solar Photovoltaic panels on a building, should take place at the architectural phase by evaluating solar panels on a holistic approach; thus taking into consideration their overall performance to the building and not just the energy they produce. Αpart from their ability to produce direct electrical energy via exposure to sunlight, Solar panels may incorporate other beneficial properties, as green building elements, such as: Thermal protection of a wall or the ceiling, Insulation, Noise dumping, Adjusting of Internal lighting and building Security. It should not be forgotten that solar panels do have the advantage of producing green energy.
Building-incorporated solar panels for home.
Undoubtedly, home solar panels (and building-incorporated solar panels in general) constitute the solution of ours and next generation homes, buildings and communities. Building roofs and glass building facades may no longer constitute an extra cost on our construction budget, but a viable, and sustainable green investment; their construction and installation cost will be financed not only by the generation of clean, environmentally friendly electrical energy, but also from the cost savings on conventional structural materials.