Overview of thermal energy storage (TES) potential energy savings and climate change mitigation in Spain and Europe
Introduction
Energy systems are complex, of uncertain behavior and not always well understood, and often, information on them is incomplete [1]. Furthermore, there is a considerable amount of waste energy in the forms of heat and cold generated each year in all types of applications, which, if properly stored, may be used at a later time or other location when required through thermal energy storage (TES). The majority of TES technologies store heat for later use in typical applications such as space heating, domestic or process hot water, or to generate electricity, though thermal energy may also be stored in the way of cold [2].
However, the benefits of thermal energy storage may not be so evident to the eye since their effects are not immediate in some cases or they are only appreciable under specific circumstances. This is why a national overview of the potential saved energy by means of using different TES systems in specific cases and its correspondent environmental effect in Spain has been carried out, broadening the overview scope to Europe. The main goal is to provide numerical proof of the energy savings in the buildings and industrial sectors, the possible reduction of waste thermal energy on a national and continental scale, respectively, as well as the associated CO2 emissions cut-down. The results and data management have been based on a previous initiative performed in Germany [3], [4], which has been employed as a model, though not the only previous study, as Wood et al. [5] had already performed a study of the TES potential (only for the industry sector) for the UK back in 1983. The here presented equations have been derived from the original model calculation sheet, and as the authors did not provide a formal calculation model. A 10-year TES scenario has been considered, assuming moderate implementation rates. The results are grouped according to application type, utilizing different parameters and obtaining the approximate annual quantity of saved energy. These values and the application are shown including the associated CO2 emissions reduction.
The objectives of this paper are: to propose a short life span scenario for the TES application near future, which presents the required numerical information in order to overview the TES potential in Spain and Europe, comparing obtained results among one another; to extend the scope of the original calculations as additional TES potential applications may be detected; and to numerically demonstrate that TES may provide significant energy and environmental benefits on national and continental scales, with little emphasis on data accuracy and/or statistical matters, but more on the potential effect of obtained results.
Section snippets
Energy sector
The following information often refers to the European Union countries (whether EU-27, EU-25 or EU-15 according to the available data) and as information about nations outside the Union is hard to find and not considered to strongly influence final desired results.
The energy sector is the largest consumer of primary energy in the EU-25. About 50% of total primary energy supply is delivered to the different sectors of energy industry. The most important of the energy sectors is power production.
Considered cases and evaluated parameters
Two main large sectors are to be distinguished: buildings and industry, each one grouping cases or sub-categories in which TES may be applied.
The cases considered for the buildings sector are seasonal solar thermal systems, district/central heating, short term solar thermal systems, and passive cold systems. As for the industrial sector the considered cases are combined heat and power (CHP, also called cogeneration), industry (heating and cooling systems), power stations and transport, and
Final results of TES potential
Global TES potential results are shown in Table 6. Numbers provided at the original German model are also presented. Since the model did not consider a 10-year scenario for all categories, original numbers have been updated in order to perform comparisons. The breakdown of the obtained values by sector and system is shown in Table 7.
A graphic comparison between the obtained results for each of the parameters has been performed. First the potential load reduction is assessed as seen in Fig. 1.
Conclusions
Based on previous work by Stricker [3], a linear model to estimate the potential TES national impact in terms of load, energy, and CO2 emissions reduction, has been formalized, the model scope broadened, its involved parameters defined and the sectors where there is actual or suitable application, described.
The task has been extended over Spain and the European Union, considering a 10-year scenario so current circumstances within the addressed sectors could be still valid and assuming low but
Acknowledgements
This work was partially funded by the Spanish government (Project ENE2008-06687-C02-01/CON). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534). The authors would like to thank Mr. Rolf Stricker for his initial feedback on the making of this work.
Glossary
- Solar collector
- It is a device designed to collect heat by absorbing sunlight for converting the energy into a more usable or storable form
- Phase change material (PCM)
- It is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus
- Heat engine
- It is an engine that performs the conversion of heat energy to mechanical
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