• Energy Research

AbstractRenewable energies can play a very important role in the development of a new energy model contributing effectively towards a more sustainable development in the mid and long term. In this context Central Solar Heating Plants with Seasonal Storage (CSHPSS) are able to provide space heating and Domestic Hot Water (DHW) to residential buildings with high solar fractions (>50%). These systems are already being used in Central and Northern Europe, as well as in Canada, where there is an important experience in district heating systems. Life Cycle Assessment (LCA) is an objective methodology that evaluates the environmental loads associated with a product, process, or activity, identifying and quantifying the use of mass and energy as well as environmental emissions over its life cycle. It provides a comprehensive view of the environmental aspects of a product or process and a more accurate picture of the true environmental trade-offs in product and process selection. In this paper is presented a LCA of a CSHPSS, which should cover the space heating and DHW demand of 500 dwellings of 100 m2, located in Zaragoza, Spain. Environmental burdens through the life cycle of the system are estimated based on relevant emissions to the atmosphere, e.g. greenhouse gases, NOx, SOx, and comprehensive environmental indicators as, for instance, the IMPACT 2002+ and CED (Cumulative Energy Demand). These indicators allow to evaluate the reduction of the environmental load achieved by the CSHPSS analyzed with respect to conventional space heating and DHW systems, as well as to identify the most critical aspects since an environmental perspective.

AbstractThe development of central solar heating plants with seasonal storage (CSHPSS) to cover part of the heating demand of buildings with district heating in the residential sector is becoming an economically viable option that can contribute significantly to the reduction of the consumption of fossil fuels. The calculation of CSHPSS systems, with a highly dynamic behaviour, is a complex process in which climatic, demand and design data are required. Simple calculation methods can be used to perform feasibility and pre-design studies enabling an estimation of the annual result. A review of several simple methods that have been proposed for the evaluation and design of the main components of CSHPSS is presented. The methods share some characteristics: main equipments considered, dependence with solar radiation and heating demand; and differ in other aspects: design parameters of the main equipments, secondary equipment considered, degree of detail of climatic and demand input data and equations of the model used to calculate the performance of the system. In this paper a description of each method is presented and results obtained for a base case (installation that produce 50% of the space heating demand for a community of 1000 dwellings in Zaragoza, Spain) are compared.

AbstractCentral Solar Heating Plants with Seasonal Storage (CSHPSS) are systems producing heat from solar radiation for a district heating system. These systems are able to produce thermal energy during all the year providing a significant part (high solar fraction) of the demands required for space heating and Domestic Hot Water (DHW). The design and calculation of the behaviour of these systems during the year is a complex process requiring detailed climatic and demand data in order to properly design/sizing the plant components to reach the desired behaviour (e.g. a specific solar fraction). The location of the plant and the different demands corresponding to different climatic areas affect very significantly the behaviour of these systems. As a consequence, the sizing and design criteria of the pieces of components of these systems are very different in the North and the South of Europe.The utilization of simple methods for the calculation of these systems allows the design of the main components and provides an estimate of the behaviour of the system during the year. In this paper is proposed a simple method for the calculation of CSHPSS using demand data and simple and easy to find available public climatic data. The proposed method is completely described and applied to specific Spanish locations to pre-design the main components of these systems. The model also provides a preliminary economic evaluation of the system and is very useful to perform parametric analysis to evaluate the CSHPSS system performance, as well as to establish optimization and design criteria of CSHPSS.

AbstractAn evaluation of Central Solar Heating Plants with Seasonal Storage in Spain has been performed with dynamic simulations built on TRNSYS. The model has been designed for several Spanish cities that are representative of the different climatic areas with a significant demand of thermal energy for heating. The system should cover the heating demand of 1000 apartments of 100 m2 in multifamily buildings with similar features, providing a solar fraction of about 50% without wasting solar heat in summer and without oversizing the seasonal storage tank. Climatic and specific demand data for each city have been used. The model simulates the solar collector field, pipe lines, heat exchangers, a seasonal storage tank, pumps, auxiliary boiler and auxiliary pieces of equipment needed in the model. The obtained results show that CSHPSS with a solar fraction of about 50% require in the case of Spain a relatively small Ratio Area of solar collectors versus heating Demand and a high Ratio of seasonal storage tank Volume versus solar collector Area. The estimated cost of the heat produced in CSHPSS with a solar fraction of 50% can be competitive with the heat cost of domestic heat boilers, which is a very common solution for heating in residential buildings in Spain. The obtained results show that CSHPSS represent an interesting and promising alternative for covering the heating demand in residential buildings in Spain.