Techno-economic evaluation of multiple energy piles for a ground-coupled heat pump system

A technical and economic feasibility study of multiple energy piles (EPs) for a ground-coupled heat pump (GCHP) system is presented in this paper. The GCHP system energy performance and life-cycle cost (LCC) are evaluated, it is found that the system energy output (heating and cooling) could meet a domestic building comfortable environment requirement with the annual average COP of 3.63 and EER of 4.62. The LCC evaluation indicates that the system net present value (NPV) is approximately £26,095 at the market discount rate of 8.75% for a 20-year operating period. Moreover, the payback period of the GCHP system is approximately 4.31 years, which is sensitive to the main parameters including electricity price, capital investment and energy generation. Furthermore, the low discount rate and high energy generation are beneficial to the GCHP system with the high NPV and cash flows. The capital price of the system should be regulated to a lower level for the larger market potential

Experimental study of a membrane-based liquid desiccant dehumidifier based on internal air temperature variation

A membrane-based liquid desiccant dehumidifier with the separated air stream and liquid desiccant channels has the ability to solve its working fluid carryover problem in the traditional direct contact system. The sensible, latent, total effectiveness and air moisture removal rate are adopted for the dehumidifier performance evaluation in this paper, and the dehumidifier main operating parameters are investigated experimentally to identify their influences and internal air temperature variations, including inlet air relative humidity (RH), inlet solution concentration and temperature, heat capacity rate ratio (Cr*) and number of heat transfer units (NTU). It is found that both the inlet air RH and solution temperature have the negative influences on the dehumidifier effectiveness, while the desiccant solution concentration has little positive influence; the air moisture removal rate rises sharply with the inlet air RH and solution concentration. The highest sensible, latent and total effectiveness achieved in this study are 0.823, 0.802 and 0.810 respectively when both Cr* and NTU are equal to 12. However the operating condition with NTU=8 and Cr*=6 is recommended with the corresponding sensible, latent and total effectiveness of 0.758, 0.71 and 0.728 respectively

CFD assessment of multiple energy piles for ground source heat pump in heating mode

Three-dimensional (3D) computational fluid dynamics (CFD) model of ground source heat pump (GSHP) with multiple energy piles (EPs) is developed to investigate the system heating performances under continuous and intermittent operating conditions, the system thermal energy outputs and coefficients of performance (COPs) are evaluated. The 3D model is meshed based on the hybrid grids with tetrahedron, hexahedron unstructured and structured types, and the k-ε equations to describe the turbulence phenomena within U-tube are resolved by using computational fluid dynamics (CFD) software. A good agreement with less than 12% difference between the CFD model and experimental results is achieved. 10 h active and 14 h idle mode is adopted as the intermittent operating condition in this study. Based on the 3D model simulation data, it is found that the average monthly COPs of the intermittent operation are 3.63, 3.58, 14 3.45, 3.21, 3.25 and 3.34 from November to April respectively, which are corresponding to 9.3%, 9.5%, 7.1%, 5.9%, 4.8% and 3.1% increases relative to those of the continuous operation. Furthermore, the soil temperature under the intermittent operating condition is higher than that of the continuous operation. To sum up, the intermittent operation not only contributes to the soil temperature recovery but also improves the system performance, which is very favourable for the long-term operation

Cost Effectiveness of Poultry Production by Sustainable and Renewable Energy Source

Poultry farming is one of high energy consumption and energy-intensive industries that requires significant amount of fuel fossil to provide the desired internal temperature for health and production level of chicken, which results in high running cost and growth of greenhouse gas (GHG) emissions. Renewable and sustainable energy technologies are being employed in the area of poultry farming in order to achieve energy saving, GHG emission reduction and to some extent supply potential selective benefits for farmers. Therefore, it is very necessary for generalizing the state-of-the-art technologies including the solar photovoltaic, solar photovoltaic/thermal, ventilation and wind turbine, air/water/ground sources heat pump and thermal energy storage. It is demonstrated that the system energy saving could achieve up to 85% with a payback time of 3–8 years, compared to the conventional heating system

Influences of the mixed LiCl-CaCl 2 liquid desiccant solution on a membrane-based dehumidification system: parametric analysis and mixing ratio selection

The membrane-based liquid desiccant dehumidification system has high energy efficiency without the traditional liquid system carry-over problem. The performance of such a system strongly depends on solution's temperature and concentration, which have direct relationship to the solution surface vapour pressure. Compared with the pure liquid desiccant solution, the mixed liquid desiccant solution has lower surface vapour pressure, better system performance and lower material cost. In this paper, the performance of a flat-plate membrane-based liquid desiccant dehumidification system with the mixed solution (LiCl and CaCl2) is investigated through theoretical and experimental approaches. A mathematical model is established to predict the system performance, while the electrolyte non-random two-liquid (NRTL) method is applied to calculate the mixed solution properties. The influences of the solution mixing ratio, temperature Tsol and concentration Csol are evaluated, and it is found that the regeneration heat Qreg can be dramatically reduced by either applying a high concentration solution or increasing CaCl2 content in the mixed solution. Compared with the pure LiCl solution system, the mixed solution system COP can be improved up to 30.23% by increasing CaCl2 content for a 30% concentration solution. The optimum mixing ratio varies with the solution concentration. For the mixed LiCl-CaCl2 solution, the system highest COPs appear at the mixing ratios of 3:1, 2:1 and 1:1 for 20%, 30% and 40% concentrations respectively

State-of-the-art review of 3DPV technology: structures and models

© 2019 Elsevier Ltd Increasing energy conversion efficiency from sunlight to power is one of the key solutions for the world's energy shortage and greenhouse gas reduction, but the conventional flat photovoltaic module without sun tracking mechanism has the low sunlight energy collection ability. This paper presents the state-of-the-art three-dimensional photovoltaic (3DPV) technology with high photovoltaic energy conversion efficiency, which is able to absorb off-peak sunlight and reflected light more effectively, thereby it can generate more power. At first, this paper is to catalogue and critique different 3DPV structures and models, as well as assess their characteristics. Afterwards, the main influence factors on the 3DPV structures and models including shape, height and spacing of the solar cells, latitude of the installation, optimal device design and shadow cast, are reviewed. Finally, the challenges and future technological developments of 3DPV structures and models are highlighted. This study demonstrated that the 3DPV technology can increase the captured sunlight approximately 15–30% in comparison with the conventional flat PV technology

A comprehensive review on 2D and 3D models of vertical ground heat exchangers

The ground source heat pumps (GSHPs) have been extensively applied to commercial and residential buildings owing to their high-energy efficiencies and low running costs. The key component of the GSHP is a ground heat exchanger (GHE). The state-of-the-art two-dimensional (2D) and three-dimensional (3D) heat transfer models for borehole heat exchanger (BHE) and energy pile (EP) systems are reviewed in this paper. The physical procedures of heat transfer and the derivation of energy conservation within different channels of BHE (e.g., U-, W-, helical-shaped or coaxial-shaped) are summarized, in addition to the primary merits and demerits of each model. The main influencing factors on 2D and 3D model solutions including axial heat transfer, friction heat, spacing shack, thermal resistance, thermal short-circuiting between the inlet-pipe and outlet-pipe, are analysed and compared. Furthermore, various applications of these 2D and 3D models are elaborated. Finally, the recommendations, standpoints and potential future research on BHE heat transfer model are highlighted. It is believed that the work presented will contribute to the record of information and experiences necessary to develop BHEs for GSHP systems

Energy performance and life cycle cost assessments of a photovoltaic/thermal assisted heat pump system

A photovoltaic/thermal module assisted heat pump system is investigated in this paper, which provides electrical and thermal energy for a domestic building. In-depth evaluation on the system energy production is conducted based on the finite difference method for a long-term operating period. The 25 years’ system life cycle cost is assessed via the Monte Carlo simulation under the Feed-in Tariff (FiT) and Renewable Heat Incentive schemes, the annual energy savings, income and payback period (PBP) are compared for the FiT and Smart Export Guarantee (SEG) schemes. The technical analysis results illustrate that the system is able to fulfil the building thermal and electrical energy demands from April to October and from May to August, respectively, and the extra electricity of 229.47 kWh is fed into the grid. The economic assessment results clarify that the system achieves a net present value (NPV) of £38,990 and has a PBP of 4.15 years. Meanwhile, the economic sensitive analyses reveal that the high discount rate reduces the system NPV whereas the high investment cost causes a long PBP to realize the positive NPV. Compared with the SEG scheme, the FiT is the most cost-effective method for renewable electricity generation and has the shortest PBP.N/

Photovoltaic/Thermal Module Integrated with Nano-Enhanced Phase Change Material: A Numerical Analysis

Solar photovoltaic-thermal (PV/T) technology is the main strategy for harvesting solar energy due to its non-polluting, stability, good visibility and security features. The aim of the project is to develop a mathematical model of a PV/T module integrated with optical filtration and MXene-enhanced PCM. In this system, a single MXene-enhanced PCM layer is attached between the PV panel and absorber pipe with solid MXene-PCM for storage and cooling purposes. Additionally, the thermal fluid is utilized in the copper absorber pipe and connected to the heat pump system for enhancing system thermal and electrical efficiency. Furthermore, the influences of the optical filtration channel height, concentration of the nanoparticles on PV surface temperature and overall system efficiency are also discussed. This study demonstrates that the annual thermal and electrical energy output can reach 5370 kWh per annum with 74.92% of thermal efficiency and 5620 kWh with 14.65% of electrical efficiency, respectively, compared to the traditional PV/T module. Meanwhile, when the optical filtration channel height and volume concentration are enhanced, they exert a negative influence on the PV surface temperature, but the overall thermal efficiency is enhanced due to low thermal resistance to heat losses and low radiation-shielding layers

Techno-economic assessment of the horizontal geothermal heat pump systems: a comprehensive review

Geothermal heat pump has been widely recognized as one of the promising technologies for building applications because of its high energy efficiency and low operating expense, however the high capital investment and installation costs discourage building owners to choose such a system. The horizontal geothermal heat pump system with reduced cost is a viable option that would be utilized widely, the aim of this paper is to catalogue and critique a range of effective approaches for the horizontal geothermal heat pump systems in different regions based on techno-economic assessment data. A ground heat exchanger is a vital component of the horizontal geothermal heat pump. The state-of-the-art analytical and numerical models of the linear-loop, slinky-coil and spiral-coil ground heat exchangers are generalized, in addition to their advantages and disadvantages. A large number of economic evaluation methods for analysing the financial performance of the horizontal geothermal heat pump system are presented. At the end, the standpoints, recommendations and potential future study on the horizontal geothermal heat pump system are deliberated