Abstract
The paper presents an innovative prototype of a solar power plant, purposely designed for small-scale applications such as residential and/or small commercial buildings. The system consists of 10 kWe Organic Rankine Cycle (ORC) plant and innovative solar thermal collectors. In particular, 235 m2 of flat-plate evacuated solar collectors are designed to heat diathermic oil up to 180°C. A variable volume pump is managed by a feedback controller in order to obtain the desired outlet set point temperature for the different weather/load conditions. The hot diathermic oil passes through a storage tank, which is adopted with the purpose to reduce the oscillations due to the solar radiation variability. By means of the tank, a better exploitation of solar energy is also achieved, reducing the time-shift between production and demand. For achieving a constant ORC inlet temperature the tank outlet hot diathermic oil passes through a gas-fired burner, which provides auxiliary additional thermal energy. Therefore, the ORC simultaneously produces electrical energy and low temperature (45°C) cogeneration heat. This solar power plant was dynamically simulated in TRNSYS environment. The simulation tool includes a novel model in order to simulate the dynamic thermal behavior of solar collectors, whereas the ORC dynamic was simulated by means of a performance data map provided by the manufacturer. The model also includes a tool for the calculation of energy and economic parameters and the evaluation of the optimum thermoeconomic configuration. Results indicated that the best pay-back period is obtained for a solar field area of about 200 m2 and a solar fraction of about 75%. Nevertheless, the system may be competitive from the economic point of view only if incentives can be made available, as commonly occurs for renewable applications, i.e., solar systems. This prototypal system aims to become a potential solar power system for small residential and/or commercial buildings. The presented study will be suitably used as a basis for the installation of a working prototype in located Naples, Italy.
Highlights
In the last decades, the remarkable consumption of fossil fuels determined severe issues concerning their future availability
The dynamic simulation shows that the system is capable to produce electricity and space heating all year long
Such solar power plant is principally affected by the solar radiation availability: During the cold winter days, when the average temperature of the fluid stored in the tank is significantly lower than Organic Rankine Cycle (ORC) inlet set point
Summary
The remarkable consumption of fossil fuels determined severe issues concerning their future availability. Several researchers focused their effort on the design and development of economically-viable technologies based on low-temperature heat sources. In this framework, special attention has been paid to develop distributed renewable power systems (solar power, photovoltaic, mini-wind, etc.) integrated in buildings (mainly residential and/or commercial) envelopes (typically roofs). In many countries, liberal policies determined the electric market deregulation, with the scope to reduce prices, support customers and promote distributed power generation. Among these innovative systems, the Organic Rankine Cycles (ORC) is commonly considered one of the most
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