Seasonal Thermal Storage System Research Articles

Experimental investigation on dynamic thermal storage and extraction performance of seasonal thermal storage

The initial investment for a buried pipe system using soil as a seasonal thermal storage medium is costly and not suitable for small rural buildings. To promote the cost-effective heating in rural areas, this study proposes a novel seasonal thermal storage system utilizing water and soil as thermal storage medium with copper rods to enhance thermal transfer between water tank and the surrounding soil. An experimental platform was established to discuss the temperature variation characteristics and investigate the thermal performance under different operating modes and experimental parameters. The results show that the temperature of the soil without copper rods is linearly related to the depth, while the highest temperature at the end of the copper rods occurs at the middle depth. The soil with short copper rods exhibits the most rapid thermal storage response and a relatively shorter thermal extraction response time. Intermittent operation can significantly enhance the thermal extraction rate and outlet temperature of the thermal storage unit, whereas the energy storage efficiency decreases with the extension of the downtime. The soil contribution rate of the thermal storage unit is influenced by the operational duration, initial temperature of the water tank and outdoor ambient temperature.

Effect of climate on the optimal sizing and operation of seasonal ice storage systems

Seasonal thermal storage systems can reduce the temporal mismatch between renewable energy availability and energy demand. Ice storage systems exhibit a non-linear behaviour in the heat exchange and storage processes, complicating the formulation of optimal design and operation problems. In this work, we propose a mixed-integer quadratically-constrained programming formulation, which minimizes the Levelized Cost of Energy for space heating and cooling, including sizing of a supporting PV array. The optimization was repeated for different storage volumes, finding the system optimal operation in each case –and thereby the optimal system sizing. The heating and cooling demands were computed from an archetypal office building, placed in three reference locations with cold and semi-arid, warm and humid continental, and temperate and humid continental climates. Results show that the optimal PV size decreases with growing ice storage volume, and an ice storage works best in a temperate continental climate, covering up to 47% of the cooling demand with a 250 m 3 storage.

A Simulation of a Sustainable Plus-Energy House in Poland Equipped with a Photovoltaic Powered Seasonal Thermal Storage System

This article describes the innovative photovoltaic powered seasonal thermal storage—PVPSTS system. It was used in the design of a plus-energy detached single-family house with a usable area of 98 m2. This area meets the requirements of the latest building regulations in Poland. The building, with the innovative HVAC installation, was subjected to energy analysis, and a numerical model was also developed. The model was tested based on TMY data for the location of Wroclaw, Poland. Analysis of the results allowed the authors to learn the specifics of the operation of the system throughout the year and to also define its efficiency. The required size of the storage stack was determined to be 1.6 × 1.6 × 0.3 m. The photovoltaic installation, which was integrated with the roof, can produce 48 GJ of electricity per year. This is five to six times more than the building’s heating needs, and any excess energy can be exported to the power grid.

Application of Borehole Thermal Energy Storage in Waste Heat Recovery from Diesel Generators in Remote Cold Climate Locations

Remote communities that have limited or no access to the power grid commonly employ diesel generators for communal electricity provision. Nearly 65% of the overall thermal energy input of diesel generators is wasted through exhaust and other mechanical components such as water-jackets, intercoolers, aftercoolers, and friction. If recovered, this waste heat could help address the energy demands of such communities. A viable solution would be to recover this heat and use it for direct heating applications, as conversion to mechanical power comes with significant efficiency losses. Despite a few examples of waste heat recovery from water-jackets during winter, this valuable thermal energy is often discarded into the atmosphere during the summer season. However, seasonal thermal energy storage techniques can mitigate this issue with reliable performance. Storing the recovered heat from diesel generators during low heat demand periods and reusing it when the demand peaks can be a promising alternative. At this point, seasonal thermal storage in shallow geothermal reserves can be an economically feasible method. This paper proposes the novel concept of coupling the heat recovery unit of diesel generators to a borehole seasonal thermal storage system to store discarded heat during summer and provide upgraded heat when required during the winter season on a cold, remote Canadian community. The performance of the proposed ground-coupled thermal storage system is investigated by developing a Computational Fluid Dynamics and Heat Transfer model.

Long Horizontal Vapordynamic Thermosyphons for Renewable Energy Sources

ABSTRACTThermosyphons of the large length are of great interest for being used as heat exchangers for recuperation of alternative energy sources and upgrading their potential with the aid of heat pumps. Some examples of vapordynamic themosyphons (VDT) application as the system of thermal control for solar collectors, in the air conditioning systems, devices combating snow drifts and icing on the active parts of the railway transport track structure, foodstuff baking ovens and roasters, driers, etc. are considered. It is concluded that VDT used for air conditioning, ground heat exchangers, and seasonal thermal storage systems connecting with solar thermal collectors have good opportunities.

太陽熱と冷暖房・給湯排熱を用いた家庭用季節間蓄熱システムに関する研究 （第3報）季節間水蓄熱槽の温度分布とシステムエネルギー性能評価

太陽熱と冷暖房・給湯排熱を用いた家庭用季節間蓄熱システムに関する研究 （第3報）季節間水蓄熱槽の温度分布とシステムエネルギー性能評価

季間蓄熱機能を有する空調システムのシミュレーションを利用したコミッショニング : 第1報-土壌蓄熱空調システムの開発と初期性能評価

季間蓄熱機能を有する空調システムのシミュレーションを利用したコミッショニング : 第1報-土壌蓄熱空調システムの開発と初期性能評価

Thermosyphons with innovative technologies

Thermosyphons of the long length are of great interest for being used as heat exchangers for recuperation of alternative energy sources (solar radiation), geothermal energy recuperation and upgrading their potential with the aid of heat pumps. In this article some examples of the use of two-phase thermosyphons in combating snow drifts and icing the active parts of the railway transport track structure, air conditioning systems, foodstuff baking ovens and roasters, driers, etc. are given. It is concluded that thermosyphons for the ground heat exchangers and seasonal thermal storage systems connecting with solar thermal collectors, are extendable to more comprehensive applications.

Limitations Imposed on Energy Density of Sorption Materials in Seasonal Thermal Storage Systems

Abstract Extensive work is undertaken in search of new materials suitable for thermal sorption storage. High energy capacity is the all sought after goal. In most cases this translates to a high maximum water vapor uptake. While this is notably important, in the system development and operation additional factors become strong contributors to the success or failure of a seasonal thermal storage system. Included are, the required system charging temperature. In domestic applications temperatures below 100 °C are most fitting to the existing building solar collector infrastructure. Further charging limitations can result from possible material characteristics such as crystallization. Just as critical as charging is discharging. It is precisely at this point where much can be gained or lost. In discharging the temperature difference between the minimum absorber temperature and the minimum evaporator temperature is critical. A low temperature difference between these two temperatures permits low resulting sorbent concentrations and thus a high accessible capacity. In a system application, these temperature levels are not freely chosen. These considerations lead to highly varying operation results in both output temperature and concentration. In this paper insight is given in respect to a sorption demonstrator plant based on sodium hydroxide as sorbent and water as sorbate.

太陽熱と冷暖房・給湯排熱を用いた家庭用季節間蓄熱システムに関する研究 （第2報）システムの年間挙動と季節槽集熱運転の検討

太陽熱と冷暖房・給湯排熱を用いた家庭用季節間蓄熱システムに関する研究 （第2報）システムの年間挙動と季節槽集熱運転の検討

Development of a Closed Sorption Heat Storage Prototype

In order to overcome limitations of solar heating, great improvements in seasonal heat storage are required. Adequate heat storage is achieved by: reducing time dependent thermal losses, reducing storage volume, and allowing easy adjustment of storage geometries to enable building retrofitting.To this purpose much theoretical and practical work has been done at Empa, including a laboratory scale proof of concept of an aqueous sodium hydroxide based seasonal thermal storage.This storage concept is based on a continuous, but not full cycle, liquid state absorption heat pump. Heat is not directly stored; instead the potential to regain heat at a desired temperature from a low temperature thermal input is stored. The main benefit is that there are no capacity losses during storage time. For this reason there is great potential in the application of the closed sorption heat storage system for long term solar heat storage. Due to the losses encountered during charging/discharging (efficiency of the heat and mass exchanger), the concept is less suitable for short term heat storage. Therefore a hybrid system is proposed, consisting of hot water tanks for short term storage and closed sorption heat storage for seasonal storage.In the scope of the EU funded project COMTES a prototype aqueous sodium hydroxide seasonal thermal storage system is under construction. The system is dimensioned to cover space heating as well as domestic hot water in a single family house built to passive energy standards and located in the region of Zurich.

Residential Solar-Based Seasonal Thermal Storage Systems in Cold Climates: Building Envelope and Thermal Storage

The reduction of electricity use for heating and domestic hot water in cold climates can be achieved by: (1) reducing the heating loads through the improvement of the thermal performance of house envelopes, and (2) using solar energy through a residential solar-based thermal storage system. First, this paper presents the life cycle energy and cost analysis of a typical one-storey detached house, located in Montreal, Canada. Simulation of annual energy use is performed using the TRNSYS software. Second, several design alternatives with improved thermal resistance for walls, ceiling and windows, increased overall air tightness, and increased window-to-wall ratio of South facing windows are evaluated with respect to the life cycle energy use, life cycle emissions and life cycle cost. The solution that minimizes the energy demand is chosen as a reference house for the study of long-term thermal storage. Third, the computer simulation of a solar heating system with solar thermal collectors and long-term thermal storage capacity is presented. Finally, the life cycle cost and life cycle energy use of the solar combisystem are estimated for flat-plate solar collectors and evacuated tube solar collectors, respectively, for the economic and climatic conditions of this study.

Smart and simple components for cost effective and robust heat exchangers

An efficient seasonal thermal energy storage system involves the use of heat-exchangers capable of transmitting power in the low-temperature region. By using a large heat transferring surface combined with multiple parallel fluid-flows in the heat exchanger also small ground stores has been found very effective both in storing chill and heat. Such a store will have the capacity to act both in a diurnal and in a seasonal thermal storage system. The Smart and Simple components are used in the ground, in the sun, in water, in floors, on roofs, in greenhouses, etc.