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The amount of installed solar power in Finland tripled in 2016, reaching 27 MWp. In Finland there are no feed-in tariffs, and with the low price of electricity together with the annual distribution of insolation concentrating on summer, the photovoltaic electricity production is economical only when used for self-consumption. When the produced electricity is used for self-consumption, optimization of the photovoltaic power system size is essential for the profitability of the investment. Usually when optimizing the size of the PV system, the electricity production is optimized so that the electricity sold to the grid is minimized. However, this can lead to undersizing of the PV power system. The PV power system size can for example be dimensioned by using methods such as the minimum energy consumption of the building, the maximum power consumption, or the net zero principle. In Finland, the smart meters provide hourly consumption data from the electricity consumers, which can be used to generate electrical load profiles. These smart meters have been installed on almost every real estate.In this paper, the profitability of a photovoltaic power system in the conditions of southern Finland is studied, simulated, and analyzed for self-consumption. Three cases, a grocery store, a dairy farm, and a domestic house with direct electric space heating, are presented and used in the simulation. Their electricity consumption is measured by hourly automatic meter reading (AMR) on a yearly basis. An Excel tool was used for the analysis of the electrical load profiles against the PV power system production at different system sizes. The profitability of the PV power system was studied by using internal interest rate, net present value, discounted payback period, and self-consumption rate. The effects of government subsidies on the profitability of a PV power system were also examined.The optimized system sizes for the grocery store, dairy farm, and domestic house with direct electric space heating were 89 kWp, 28 kWp, and 5.2 kWp, respectively. The solar modules of the grocery store and the domestic house were facing south whereas the optimal module orientation in the dairy farm was 50-50% east-west. It was found that in the case of the grocery store and the dairy farm, the PV system size could be increased without the internal rate of return decreasing significantly, and thus, a larger system could be justified. Using the self-consumption ratio to optimize the PV power system size leads to undersizing of the system. It was found that the subsidies for the PV power systems have a significant impact on profitability. In the cases of optimized sizes, the grocery store would be economically viable even if the electricity price decreased annually by 3.6% with subsidies and 1.0% without subsidies. The optimized PV power system of the dairy farm would be economically viable if the electricity price decreased by 3.3% annually; however, without subsidies the electricity price would have to increase by 1.0% annually to remain viable. Co...

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Abstract-Fluid handling systems such as pump and fan systems are found to have a significant potential for energy efficiency improvements. To deliver the energy saving potential, there is a need for easily implementable methods to monitor the system output. This is because information is needed to identify inefficient operation of the fluid handling system and to control the output of the pumping system according to process needs.Model-based pump or fan monitoring methods implemented in variable speed drives have proven to be able to give information on the system output without additional metering; however, the current model-based methods may not be usable or sufficiently accurate in the whole operation range of the fluid handling device. To apply model-based system monitoring in a wider selection of systems and to improve the accuracy of the monitoring, this paper proposes a new method for pump and fan output monitoring with variable-speed drives. The method uses a combination of already known operating point estimation methods. Laboratory measurements are used to verify the benefits and applicability of the improved estimation method, and the new method is compared with five previously introduced model-based estimation methods. According to the laboratory measurements, the new estimation method is the most accurate and reliable of the model-based estimation methods.

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