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S M A R T  -  E N E R G Y  -  S Y S T E M S



Our credo: Energy supply with local renewable energy. But is an independent energy supply also possible for you? The answer is YES. And how this energy solution can look in detail is explained by a typical household of a family of four in Central Europe:


Electricity consumption per year: approx. 4,000kWh

Heat energy demand per year: approx. 20,000 kWh (equivalent to 2,000 liters of heating oil)

Energy demand for mobility (30,000 car km) per year: about 4,500kWh for electric cars and about 13,500kWh (equivalent to 1,350 liters of gasoline / diesel) for gasoline / diesel cars



(1) The electrical energy consumption is about 4,000kWh per year. One year has 8760 hours - resulting in an average consumer power of around 0.45kW (0.45kW x 8.760h = 4.000kWh). In fact, however, the average daily consumption fluctuates considerably over the course of the year. In winter, the average daily consumption increases to about 14.60kWh (= 0.60kW x 24h), while in summer the average daily consumption decreases to about 7.30kWh (= 0.30kW x 24h):




(1a) A typical 4kW photovoltaic system with around 27m² of PV module surface and 45 ° module inclination towards the south generates around 4,000 kWh of green electricity per year in Austria. However, the lowest average daily yield is 3.6kWh (= 0.15kW x 24h) in winter and the highest average daily yield is 18kWh (= 0.75kW x 24h) in summer:






A typical 4kW photovoltaic is therefore not sufficient to cover the above-mentioned power requirements of a single-family household, since in winter only about a quarter of the actual required electrical energy consumption can be generated.



(1b) On the other hand, with a demand-oriented photovoltaic system with around 80m² of PV module surface and 65 ° module inclination towards the south, the electricity requirement for a single-family home can very well be generated all year round:




(1c) If the typical 4 kW photovoltaic system were to be quadrupled from (1a) to 108m² (= 4 x 27m²), the power consumption of a single-family home could also be covered. However, in the summer around 10 times as much green electricity would be generated as necessary:


On the other hand, (1b) only four times more than the actual electrical energy requirement.




(1d) In addition to solar energy, of course, wind energy can also be used on site. At a typical mean wind speed of 4m / s, a small wind power plant (rotor area 30m²) generates around 4,000kWh per year:



It is striking that the annual average power output of a (small) wind turbine corresponds in good approximation to the average annual power consumption of a typical family of four in Central Europe.



Conclusion: With a demand-oriented sized photovoltaic system or small wind turbine with electrical energy storage (lithium-ion battery) with about 75kWh (storage capacity for about 4 to 5 days in winter) can provide a typical household of a family of 4 in Central Europe self-sufficient with electrical energy , Note: In a combined energy solution of photovoltaic (2,000 kWh) and wind power (2,000 kWh), the capacity of the energy storage can be reduced by about 30%.




(2) The heat energy demand of a typical household of a 4-member Central European family amounts to approximately 2,000 liters of heating oil (equivalent to 20,000 kWh = 2,28 kW x 8,760) per year or it is emission-free on site with a groundwater heat pump including a small wind turbine (or PV system). Plant) and electrical energy storage generated. In winter, the average heating and hot water demand reaches up to 103kWh (= 4.26kW x 24h) per day, whereas the mean heat energy demand in summer (only for hot water treatment) drops to 7.3kWh (= 0.30kW x 24h) per day:





(2a) Property owners with groundwater resources can also be happy with regard to local renewable heat energy. Even a typical garden water pump, with a volumetric flow rate of around 2,500 l / h, can supply enough groundwater to cover the heat requirement of a typical household of a family of 4 Central Europeans. After the groundwater warms up a few degrees over the summer months (from about 8 to 12 ° C, depending on the local situation), at the beginning of the heating season in the fall, the greatest thermal energy potential is around 520kWh (= 22kW x 24h) in the groundwater - for use a conventional heat pump, the water can be cooled to about 4 ° C:


On a really cold winter day, up to 396kWh (16.5kW x 24h) of heat energy from the groundwater is available for heating purposes. This corresponds to a boiler with a heat output of 16.4 kW.



For the operation of a modern groundwater heat pump around 1/5 (= inverse of the coefficient of performance of a heat pump) of the generated heat output in the form of electrical energy for compressor and circulating pumps is needed. For the above heat demand of a typical household of a family of 4 in Central Europe, the following electrical power requirement for the operation of the groundwater heat pump results:


The required electrical energy for the groundwater heat pump can be generated on site without too much energy surplus in the summer by a small wind turbine 



or with significant energy surpluses in the summer by a photovoltaic system.





(3) It is well known that energy consumption for mobility can be significantly reduced by public transport (many people in a vehicle). Short distances on foot or by bicycle are also suitable as a daily exercise for a general well-being. In the countryside, however, a private car is often the only way to travel longer distances to remote areas.

Depending on the cw value, the energy requirement of a car at a driving speed of 100km / h in one hour is about 15kWh for an electric car and about 45kWh (4.5 liters) for a gasoline or diesel powered car.

In detail, the energy balance looks like this:


                                                                                                        Electric car                     petrol / diesel car


Air resistance (airstream)                                                               10kWh                             10kWh

Rolling resistance tire                                                                       2kWh                                2kWh

Electric motor                                                                                    0,5kWh

Power electronics                                                                             0,5kWh

Battery storage (charging / discharging)                                        4kWh

Gasoline / diesel engine                                                                                                            33kWh

Total consumption                                                                             15kWh                             45kWh



Particularly at higher speeds, the air resistance (wind) to be overcome is decisive for the energy consumption of a modern vehicle:


If a 4-headed Central European family covers 30,000 km of car travel per year, then 4,500kWh for an electric car or 1,350 liters of fuel (13,500kWh) for a gasoline or diesel car with additional energy is needed. Normally, energy consumption for mobility is distributed evenly throughout the year:


In this respect, for the operation of an electric car on average about 12.3kWh (= 0.51kW x 24h) of electrical energy is needed per day, ideally generated on site in equal parts (2x 2.250kWh) from a combination of small wind turbine and photovoltaic system should.




This case study shows that the combination of wind power and geothermal energy in particular enables demand-oriented energy supply in Central Europe.

On the other hand, photovoltaics provide considerable green electricity surpluses in the summer, while hydropower, which has not yet been considered, generates green electricity surpluses in the spring. If you want to feed in or sell the green electricity surpluses in the public grid, you have to expect high payments in form of network fee and green electricity. These installment payments can then be used to finance long-term energy storage systems, such as pumped-storage power plants, which, for example, can transfer energy surpluses from the summer months into the winter months.



For advice, planning and project implementation of your energy project we are at your disposal.