Vertical-borehole ground-coupled heat pumps: A review of models and systems

General review of ground-source heat pump systems for heating and cooling of buildings

Thermal energy storage (TES) is an advanced technology that could address the energy supply-demand balance in building air conditioning systems. TES is also important in view of the increasing utilisation of solar energy. Although sensible heat storage systems and latent heat storage systems have been heavily researched and are widely used domestically and industrially, thermochemical heat storage (THS) systems are currently undergoing a surge in research and development. Recent studies suggest that THS has significant advantages when compared with the other heat storage methods including higher storage density, lower volume requirements, low heat loss (approaching zero), and lower charging temperature. On the other hand the complexity and higher investment costs remain the main obstacles to rolling out these systems commercially. A comprehensive review has been presented here into all aspects of the current, state of the art THS research. It includes comparisons with other storage methods, description of absorption/adsorption cycles, the materials used in these systems and open/closed storage methods, as well as chemical heat pumps. Recent advances in the field are also investigated and discussed.

The latest advancements on thermochemical heat storage systems

Model Predictive Control (MPC) can be used to control a system of energy producers and consumers in a Smart Grid. In this paper, we use heat pumps for heating residential buildings with a floor heating system. We use the thermal capacity of the building to shift the energy consumption to periods with low electricity prices. In this way the heating system of the house becomes a flexible power consumer in the Smart Grid. This scenario is relevant for systems with a significant share of stochastic energy producers, e.g. wind turbines, where the ability to shift power consumption according to production is crucial. We present a model for a house with a ground source based heat pump used for supplying thermal energy to a water based floor heating system. The model is a linear state space model and the resulting controller is an Economic MPC formulated as a linear program. The model includes forecasts of both weather and electricity price. Simulation studies demonstrate the capabilities of the proposed model and algorithm. Compared to traditional operation of heat pumps with constant electricity prices, the optimized operating strategy saves 25–35% of the electricity cost.

Economic Model Predictive Control for building climate control in a Smart Grid

Magnetorheological (MR) materials are classified as smart materials due to their responsiveness to external magnetic stimuli. Intensive research on MR materials has led to broad applications in several potential fields. A solid carrier matrix state called MR elastomer with its exceptional magnetic responsive feature is obtained by merging magnetizable particles within an elastomeric polymer. This integration results in outstanding characteristics on the rheological performances. Special prominence is given to the understanding of the base materials and fabrication as well as the functional behavior through various characterization methods. Broad applications of MREs are also explored to provide a profound market picture and to motivate researchers to develop novel technology. The functional behavior of MREs is briefly explained. The art of the materials provides the current position and mapping of the matrix and filler particles. Types of matrix and particles are mentioned together with the level of the research interest on MREs. Description of the fabrication is provided in simple diagrams as summarized from previous works to enhance the MREs performance. The possible tests to reveal the characteristics of the MREs are delivered with the global experimental setup. The review also explains the applications of MREs as well as discussion on the MREs future promising applications.

Recent Progress on Magnetorheological Solids: Materials, Fabrication, Testing, and Applications†

Numerical simulation of solar assisted ground-source heat pump heating system with latent heat energy storage in severely cold area

Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 °C higher than the original one after one year’s running. It is beneficial for the system to operate for long period.

Simulation of embedded heat exchangers of solar aided ground source heat pump system

In solar aided ground-source heat pump (SAGSHP) system with soil storage, heat collected by solar energy in three seasons was stored in soil by vertical U-type heat exchangers. Heat extracted by the ground-source heat pump combined with the heat collected by the solar collector is employed to heating. Some of the soil exchangers are used to store solar energy in the soil so as to be used in winter after heating period; the others are used to extract cold in the soil by circulation pump for air conditioning in summer. Low temperature radiant floor (ceiling) heating and cooling air conditioning system which can highly meet personal thermal comfort is used indoor. The temperature SAGSHP supplied is just suitable for the requirement of low temperature radiant system. Numerical simulation was done for low temperature radiant floor (ceiling) air conditioning system, how temperature of cold water affects floor temperature and ability of heat transfer was studied and also variation and restoration of soil temperature was researched. It indicates that economy, reproducibility and reliability of SAGSHP system are obvious. It can run for many years.

Fang Wang

Papers

Numerical simulation of solar assisted ground-source heat pump heating system with latent heat energy storage in severely cold area

Simulation of embedded heat exchangers of solar aided ground source heat pump system

Numerical simulation of heating & cooling air conditioning system of solar aided ground source heat pump system with soil storage