Renewable Energy Sources
Renewable Energy Sources (RES) – this is a new branch of power engineering which implements the assumptions of sustainable development, i.e. minimising the extraction and production of electrical energy from the combustion fossil fuels, and hence lower carbon dioxide emissions. RES systems in typical households include photovoltaic cells (PV) and small wind power plants (SWPP). Their installation in typical households is not complicated and does not require building permits in the majority of cases.
Detailed conditions of RES installation
With regard to the most common roof constructions (flat or sloped), the following methods are used for the installation of photovoltaic panels:
1. No interference in the roof construction is expected in the case of a flat roof. The proposed frames keep the panels fixed at the correct angle (30 to 50 degrees in the north of Poland). It is also important that the panels face south to take best advantage of the sun's position in the sky in order to maximise solar radiation throughout the day.
2. Installation on a sloped roof is possible only if that part of the roof where the system will be installed faces south. In order to install the system it will be necessary to fix the mounting frames to the roof; the type of the frame depends on the roof covering. The mounting systems are designed so that leaks or any other damage to the roof is prevented.
Besides mounting the panels on the roof, an inverter (the device which converts solar radiation into electrical energy) has to be installed indoors, either in an attic or basement. The inverter may be installed near a switch cabinet. When selecting an appropriate location, it is important to remember to leave some free space on either side to ensure ventilation and service access. All the equipment must be connected up using cables, along with a device in the switch cabinet to allow for PV system disconnection, if required.
With regard to the most common roof constructions (flat or sloped), the following methods are used to mount wind microturbines:
1. Mounting on a roof
The mounting frames have to be fixed to the roof frame. A post is then installed and the turbine fixed to this. The turbines come ready to install from the manufacturers and their mounting on the roof does not result in vibrations being transmitted to the building structure or onerous noise.
2. Mounting on a post
When mounting a turbine on a post it is necessary to interfere with the roof construction. The post to which the turbine is mounted is fixed to the facade of the building using four mounting bolts. The turbines come ready to install and do not transmit vibrations to the building structure or cause onerous noise.
Influence of microsources on energy consumption
Within the ENERGA Living Lab Project, microsources in the 1-1.3 kW power range have been installed in the participants’ households. According to the project assumptions of using some pieces of equipment when energy is cheaper, all RES microsystems come with 4 batteries to store energy. They supply some equipment during the day, taking power from the grid once the batteries are depleted.
It is assumed that the efficiency of a photovoltaic system reduces by 2.5% in the first year and by 1% every subsequent year. The power generator capacity remains almost unchanged in the case of a wind micro power plant.
Sunshine has a great influence on the efficiency of photovoltaic microsystems. The average annual sunshine in the Pomerania Region is about 900–1000 kWh/m2. The distribution of solar radiation is not uniform in the annual cycle, with about 80% of the annual sunshine occurring in the spring and summer period (April – September).
Wind capacity is the equivalent to the sunshine parameter in the case of wind microturbines. The average annual wind speed is about 10 m/s in northern Poland. The Pomerania Region is located in the highest wind power zone, which makes it one of the most favourable locations for wind power plants in Poland.
Diagram of RES influence on a household
A typical household with an annual energy consumption of 2500 kWh was assumed, and the diagram developed based on a fixed electrical energy rate assuming that annual power consumption does not change. The RI will accelerate when the expected legal facilities become effective.
Possibility of extending the RES
The total power of the microsources installed within the Project is 1 kW, which requires an inverter with a rated power of 1 kW or slightly higher to meet the requirements of effective operation. After the end of the Project, the participants can keep the installed system free of charge and may modify the previously used PV system and extend it by adding a higher capacity inverter and additional panels.
In order to connect a microsystem to the grid, the natural person being its owner or an appointed representative reports the fact of building a microsource to the distribution system operator (ENERGA-Operator). Then, both parties sign an agreement regulating the distribution and sales of electrical energy. In order to announce the connection of a microsystem, you must fill out an application for a microsystem connection. The application forms are available on the ENERGA Operator website. Specimens of applications and forms can also be obtained at the Connection Service Point. ENERGA-OPERATOR SA will verify the microsystem and send information on the possibility of signing an agreement for providing electrical energy distribution services. Based on the information on the possibility of signing an agreement for providing electrical energy distribution services an agreement will be signed with ENERGA-OPERATOR SA, forming the grounds for distribution of the electrical energy generated by the microsystem. If you intend to sell electrical energy introduced to the power grid from the microsystem, you have to sign an agreement for selling electrical energy.