Dynamic simulation tool for a performance evaluation and sensitivity study of a parabolic trough collector system with concrete thermal energy storage

Plant developers of parabolic trough collector (PTC) systems for industrial steam generation face various challenges. Some of the main challenges are availability of land, buildings in the vicinity of the plant that cast shadows on the collectors as well as land restrictions. The typical north-south collector axis alignment in many cases may not be possible due to limits of available ground. These were challenges that were faced in the planning phase for installing a PTC plant on the premises of the KEAN Soft Drinks Ltd factory in Limassol, Cyprus. As these issues cannot be avoided they must be accounted for by the plant developer, especially when a performance guarantee is given. This work presents, amongst other things, factors that should be analysed in order to predict the energy yield in the planning phase as best as possible by using a simulation model. In the sensitivity study presented in this paper, several effects on the energy yield were investigated theoretically. These effects include: Tracking inaccuracy, non-parallel collector row axis orientations as well as north-south vs. east-west collector alignment. A dynamic simulation model developed by the Solar-Institut Jülich (SIJ) [1] was further developed and used for the analysis. The simulation model features a deviation between the measured and simulated oil temperature at the collector outlet of only 1.5 K (rms). The findings are presented in this paper and give an insight into the effectiveness of mid-sized PTC systems for the industry sector

Operational experience and behaviour of a parabolic trough collector system with concrete thermal energy storage for process steam generation in Cyprus

As part of the transnational research project EDITOR, a parabolic trough collector system (PTC) with concrete thermal energy storage (C-TES) was installed and commissioned in Limassol, Cyprus. The system is located on the premises of the beverage manufacturer KEAN Soft Drinks Ltd. and its function is to supply process steam for the factory’s pasteurisation process [1]. Depending on the factory’s seasonally varying capacity for beverage production, the solar system delivers between 5 and 25 % of the total steam demand. In combination with the C-TES, the solar plant can supply process steam on demand before sunrise or after sunset. Furthermore, the C-TES compensates the PTC during the day in fluctuating weather conditions. The parabolic trough collector as well as the control and oil handling unit is designed and manufactured by Protarget AG, Germany. The C-TES is designed and produced by CADE Soluciones de Ingeniería, S.L., Spain. In the focus of this paper is the description of the operational experience with the PTC, C-TES and boiler during the commissioning and operation phase. Additionally, innovative optimisation measures are presented

Simulation of a solar domestic water heating system using a time marching model

This paper presents the modelling and simulation of a solar water heating system using a time marching model. The results of simulations performed on an annual basis for a solar system, constructed and operated in Yugoslavia, which provides domestic hot water for a four-person family are presented. The solar water heater consists of a flat-plate solar collector, a water-storage tank, an electric heater, and a water-mixing device. The mathematical model is used to evaluate the annual variation of the solar fraction with respect to the volume of the storage tank, demand hot water temperature required, difference of this temperature and preset storage tank water temperature, and consumption profile of the domestic hot water demand. The results of this investigation may be used to design a solar collector system, and to operate already designed systems, effectively. The results for a number of designs with different storage tank volumes indicate that the systems with greater volume yield higher solar fraction values. The results additionally indicate that the solar fraction of the system increases with lower hot water demand temperature and higher differences between the mean storage water and the demand temperatures. However, when a larger storage tank volume is used, the solar fraction is less sensitive to a variation of these operation parameters

Potential of the parabolic trough collectors use in the industry of Cyprus: Current status and proposed scenarios

Cyprus is the worldwide leader country for the use of solar water heating systems per capita, which are of the thermosiphon solar water heating type. In this paper, an investigation of the perspective to start using parabolic trough collectors (PTC) is carried out. The idea to use PTC systems is still new in Cyprus since there are no installations and it is not a well-known technology yet, but it could create a good prospect by starting from the large industries of the island. Although the industrial market of Cyprus is small, the large amount of incident solar radiation throughout the year and the need of the people to reduce their energy needs, makes the idea to adopt PTC collectors for energy production very tempting. Most of the industries use thermal and electrical energy for their various processes, with the biggest consumer to be the nonmetallic minerals industry (glass, pottery and building materials) and the second bigger consumer the food industry. The latter requires large amount of thermal energy which could be provided by PTC since the required temperatures are 120°C - 250°C which is very common range of temperatures for such systems. Thus, parabolic trough collector systems could be a sustainable, profitable and dispatchable technology, especially for the Cypriot industries. This study presents an investigation carried out to summarize the current status of the industrial energy needs as well as the systems being used for energy production currently. Accordingly, an examination of the PTC systems is done in order to identify the potential of installation of such a system in a case study from the industrial sector, considering the energy production, the cost of installation and cost of energy savings as well as the CO2 emissions reduction. Finally, a discussion is made on the potential of the Cypriot industry to use PTC collectors analyzing the pros and cons of such applications

A pilot PTC system installed in an industrial factory of Cyprus: Feasibility for the wider use in the Cyprus industry

A total of 94 % of the energy demand in Cyprus is covered by consuming fossil fuels. Sectors such as transportation and industry are the biggest consumers, corresponding to a consumption of 57 % and 20 % respectively. Apart from the environmental impact from the use of fossil fuels, fuel cost has a direct impact on the country's economy as well. Based on these facts and having as a goal to reach the EU 2020 energy efficiency target, an effective way to reduce the use of fossil fuels and energy consumption, is the use of renewable energy systems. Moreover, it was revealed that the biggest energy consumer from the industrial sector is the food and beverage industry. Solar energy systems that could support the thermal energy needs of these industries are small-scaled middle temperature parabolic trough collectors (PTC) with thermal storage and auxiliary systems. The purpose of this study is to present the first pilot PTC system installed to serve 40 kWth of the thermal needs of a soft drink factory named 'KEAN', located in Limassol, Cyprus. A dynamic simulation modelling is also developed to predict the performance of the system and study its potential to be further utilized in a higher thermal load. For the dynamic modelling of the system, TRNSYS software is used, with weather data from typical meteorological year (TMY) files for Cyprus. It was concluded that KEAN solar system could produce 125 kWth heat from which the 40 kWth are utilized by the industry whereas the rest are stored and used when needed. For a bigger application, for a dairy factory, a year period, and a thermal load of 190 kWth the system with 42 collectors could cover 68% of the load and the auxiliary covers the rest. To examine the potential of this system a life cycle cost analysis (LCCA) has been done. It was concluded that the total investment would have a payback period of 5 y

A design tool for a parabolic trough collector system for industrial process heat based on dynamic simulation

The industrial sector is one of the biggest oil consumers in Cyprus, corresponding to 20% of the fuel consumption. A parabolic trough collector (PTC) system seems the best option to produce clean thermal energy at higher temperatures than those that can be achieved from the already widely used flat plate collectors on the island. This paper presents a simulation model built to investigate the performance of the first industrial PTC system in Cyprus, installed at the Cyprus biggest soft drinks factory. The simulation model is built in TRNSYS and is validated using data from the real PTC system installed at the factory. The results show a very good fitting between the operating parameters and the power output of the Solar Field (SF), Concrete Thermal Storage System (CTES), and the Steam Generator (SG). The average percentage relative error of the system's contribution to the process is less than 6.32% for the daily steam production and during a week did not exceed 6.45%. The novelty of this study is the development of a design tool that can be used by potential interested industries to identify the suitable system that fits their needs. All data are provided in the form of graphs and allow anyone to use as input data the thermal energy demand and required steam temperature of the industry to retrieve information about the size of a suitable system which satisfies these requirements depending on each case. The payback period for all cases examined varies from 2 to 6 years, depending on the size of the system

Experimental performance of a parabolic trough collector system for an industrial process heat application

The authors regret to realise a typing mistake on page 3, line 9. The number of 280 kWth should be 280 kWhth. Additionally, there is a problem in Fig. 5. The correct figure and the correct legend of the figure are as shown below: [Figure presented] Fig. 5. (a) Steam generator (b) feed water tanks (c) variable speed pump (d) control valves. The authors would like to apologise for any inconvenience caused.Manufacturing is responsible for 60% of the fuel consumption in Cyprus and the industrial sector is the second biggest fuel consumer, mainly for steam production. Thus, the use of parabolic trough collector (PTC) systems for the production of steam or hot water can be a promising solution for the industrial sector. This study presents the first industrial PTC system in Cyprus, installed at the biggest soft drinks factory. The system consists of 288 m2 of PTC, a steam generator and concrete thermal energy storage (CTES) in order to keep the system dispatchable. To achieve that, two operation strategies are developed which are controlled automatically by the main processor of the system. The first strategy is enabled when there is a steam demand and the second when the energy can be stored directly to the CTES. Both strategies are tested, and it is shown that under Strategy 1 the PTC system can produce 940 litters of steam per day, and under Strategy 2 it can store 107.3 kWhth. In two months period tests, it is proved that it can supply the required amount of steam to the factory even when solar radiation is low, with the support from the CTES