The construction of photovoltaic plants permits to use solar Energy to convert it in electricity by photovoltaic effect. The main components of photovoltaic plants connected to the network are:
- Photovoltaic field: deputed to convert solar Energy by photovoltaic modules placed efficiently facing the sun.
- Inverter: deputed to stabilize gathered energy, convert it in alternating current and feed it into the grid.
- Protection and control panel boards, to settle under current regulations from the inverter and the alimented network.
- A component often underestimated, connecting cables, they have to be UV and high temperature resistant.
The area covered by a photovoltaic plant is mostly slightly larger than the area covered only by the photovoltaic modules, that requires, with today's technologies, around/about 8 m2 / kWp which are added potential areas covered by the shadow cones of the modules, when arranged not in a coplanar way.
To be noted that every cell typology has a typical "consumption" in terms of area, with amorphous silicon technologies is over 20 m2 / kWp. On ground installations or flat roof, it is common practice to geometrically dispose the field in several rows, appropriately singular raised towards the sun, in order to maximize the received radiation from modules. These rows are laid for geometric needs of the installation site and can or cannot match with electric strings, or rather serieses, laid instead for electrical system requirements.
Moreover to maximize the received sun radiation we plan and implement many more "tracking" sun photovoltaic modules that adapt the receiving panel inclination to sun's rays during the day and season.
A special mention goes to the so-called BIPV, acronym of Building IntegratedPhotoVoltaics. The architectural integration is achieved arranging the photovoltaic plant field inside the profile of the building that hosts it. The techniques are mainly 3:
- Local replacement of the roof cladding (e.g. flat or curved tiles) with a suitable coating that is overlapped from the photovoltaic field, so that results fixed in the roof cladding.
- The use of appropriate integration technologies, as thin films.
- The use of structural photovoltaic modules, that integrate the infixed function, with or without double glazing.
Wind energy is the product of the conversion from kinetic energy to electric one. This conversion is made by a wind central unit. The uses is made by wind machines which are divided into two distinct groups by the type of base module used called wind turbine generator: Eolic generator at vertical axis and eolic generator at horizontal axis.
It is designed to take into account of both a centralized production of plant placed in high and ventilated locations, also a potential energy decentralization, for which every Town has small plants, made of a low number of windmill blades (2-3 blades of 3-4 megawatt) With which can generate on site the used energy of its habitant. The plant installation time is very short; after making the field surveys to measure the wind speed and the power that can be generated, the blades have to be transported and placed on ground.
The planning and building time of other stations ( hydroelectric, thermoelectric etc.) is longer than 4 years. Despite the best of intentions, the absence of frame rules or a consolidated law on wind power, contrary to sun power, is seen as one of the causes of the slower diffusion of technologies than abroad.
Although the wind power is the less expensive Energy, it is neither requested from electric manufacturers that could resell it at the kWh actual cost with largest profits, nor the first Energy quantity to be sold on the power Exchange that combine supply and demand of energy based on the electric kWh price (the wind power, having the lower price per kWh is convenient and should be easily positioned).
The wind power plant is composed by one or more wind turbines that uses the same principle as windmill: the wind pushes the blades. But in the case of wind turbines the rotation motion of blades is transmitted to a generator that produces electricity. There are different wind turbines in form and size.
The solar collector or solar panel is the basic device on which is based this the technology. The collectors are crossed by a heat carrying fluid channeled in a solar circuit that leads it to an accumulator. The accumulator has the function to store more thermal Energy possible in order to use it when it's needed. There exists several types, the latest are vacuum tubes that have a high efficiency and are subject to breakups.
A solar thermal system is made up of at least the following units:
- One or more collectors that give off the solar heat to the fluid; there are several types, from a simple copper plate crossed by a serpentine and painted with black varnish, to a selective panel treated with titanium dioxide (TINOX) the vacuum-sealed absorber. In the first two cases the absorber is protected with a toughened glass, that can be prismatic.
- A fluid storage tank.
There are two type of plants:
- With natural circulation: in this type of fluid it's the water that heating rises for convention in a storage tank (boiler), that has to be placed above the panel, from which is supplied to the domestic users; it's an open circuit, as the water that is consumed is replaced from the external flow. This plant has an advantage in its simplicity but is characterized by a high heat loss, at the expense of efficiency.
- With forced circulation: It is a circuit composed of a panel, a serpentine inside the boiler and connecting pipes. A pump, called circulator, allows the transfer of the heat gathered by the fluid, in this case propylene glycol, similar to ethylene glycol (liquid used for car radiators), to the serpentine inside the boiler. The circuit is considerably complex, it provides an expansion tank, a temperature control and other components, and has an electric consumption due to the pump and the control unit, but it has a higher thermal efficiency, since that the boiler is inside and is less susceptible to heat loss during night or adverse weather conditions.
The cogeneration is a process that allows the simultaneous production of two different energy forms (e.g. electric and thermal), starting from only one energy source. This allows to achieve a more efficient energy production process and a cleverer use of the source, achieving a significant energy saving. The estimate Energy saving possible to achieve by the cogeneration varies on average between 20% to 40% compared to the uses of two different plants that produce electric and thermal energy. Cogeneration plants are essentially made by four elements: The main engine, the generator, a thermal recovery system and electricity interconnections.
The cogeneration process allows an efficient use of fuel 80% higher with a following containment of polluting gasses emissions. The most widely used, checked and highly reliable typology of engine system implemented in cogeneration plants is the endothermic engine. The cogeneration is typically called "micro-cogeneration" for power up to 50 kWe and "small scale cogeneration" up to 1 MWe. The endothermic engine cogeneration system, together with a heat distribution system, is able to produce mechanical work, electricity, heating also for civil or industrial uses in low temperature, giving high efficiency levels. In short, with the use of absorption chillers is possible to integrate the thermal process to generate also frozen fluids (trigeneration). The cogeneration plant, if requested, can be placed inside a soundproof container, installed outside, or placed inside a central heating plant environment already existing. The site choice is typically dictated both by sizing requirements and by security and visual and acoustic impact needs. They will be established and followed by all the necessary procedures to obtain various financial and incentive facilitations provided at community, national and local level present at the time of realization and building of the cogeneration plant
elevant technologies founded by the increasing of the Energy efficiency in the civil field are the ones related to the casing (air conditioning, insulation and/or other building operations), the lighting, the plant efficiency ( generating electricity, to the cogeneration/regeneration, including the micro-cogeneration and distributed generation), the domestic appliance and the ict/automation (building automation). Of particular interest is the intervention concerning the air conditioning, insulation and lighting, fields that give immediately the greater returns with the current technologies. The air conditioning and insulation refer to the casing solutions; the thermal insulation is the most efficient and economic solution for the reduction of the heating requirement.
Generally when we talk about insulation we think about cold insulation and less about the behaviour of the building during the summer: actually both periods have to be taken into account as they are energy consuming.
The reduction of energy spending implies project choices that consider winter and summer requirements. For winter time the energy balance takes into account the building size and profits in terms of free energy supplies. It needs to be considered thermal exchanges by transmission (towards the outside, the ground, adjacent rooms with lower temperature or not heated) and by ventilation (toward the outside and heated rooms with lower temperature or not heated). The solar supply is due to the solar radiation on opaque walls and on window surfaces in addition to the supply related to the activity developed inside. Almost 80% of the heating of the cooling pass through walls, rooves and attics and the remaining part is due to uncontrolled air currents, produced by bad holding or cracks in doors and windows.
There are several technical solutions and use of materials as isolation systems of vertical walls and flat roves, inclined or towards non-heated rooms and earth retaining walls which are both technical solutions and usable material. There are three are the intervention techniques that refer to the location and the way to apply the insulating coating: On the inside or the outside of the building or in the cavity of the brickwork. All of them have different materials and/or modes of application with advantages and disadvantages.