Flexibility Services to Minimize the Electricity Production from Fossil Fuels. A Case Study in a Mediterranean Small Island

The aim of this study was to test a tri-partite gas cooler for CO2 heat pumps (5-13 kW). The proposed heat exchanger allowed the simultaneous and separate production of space heating and domestic hot water with an integrated design, simplifying the heat pump layout and piping requirements. The experimental campaign was dedicated to the performance of the gas cooler at various operation conditions. These operation modes are: i) only space heating, ii) only domestic hot water iii) simultaneous production of domestic hot water and space heating. The results of the test campaigns were analysed in order to determine potential improvements or required redesign of the heat exchanger. The heat exchanger solution was integrated to novel prototype of tri-generation CO2 heat pump system.

Influence of the refrigerant charge in an R407C liquid-to-water heat pump for space heating and domestic hot water production

Performance analysis of a R407C liquid-to-water heat pump: Effect of a liquid–vapor heat exchanger and domestic hot water production

Analysis of the impact of different operating conditions on the performance of a reversible heat pump with domestic hot water production

Systems based on the coupling of heat pumps (HP) with solar hybrid photovoltaic and thermal technology (PVT) for domestic hot water (DHW) production are a valid alternative to conventional electric production systems. In previous research, simulation models were developed in order to study the dynamic behaviour of a plant set-up based on the integration of an air-to-water heat pump aimed at DHW production with a rated power of 700 W and a storage tank of 500 lt. It was coupled with a plant of 6 PVT flat uncovered hybrid solar collectors with a peak power of 300 W for each module. Starting from the results obtained in the pre-sizing stage, in this study, a plant configuration was analysed to maximize the exploitation of the low-temperature contribution provided by the adopted PVT collectors. With this aim, the efficacy of the introduction of a solar water preheating storage in addition to the one normally integrated into the HP was investigated. Different operational scenarios have been studied to evaluate the best energy management strategies to be implemented. They consider the influence that the thermal capacity of the solar storage could have on the system performance according to its volume and the setpoint temperatures. The obtained results show that the proposed plant solution generally allows an increase in solar energy exploitation for DHW production and a reduction in HP electricity consumption.

In last years, the energy efficiency in non-interconnected islands became an important topic, since the electricity production is often based on diesel generators, thus contributing to the global warming. Italian government recently emitted two decrees to promote the introduction of renewable energy technologies in 21 non-interconnected islands, both for electrical and thermal uses. In this paper, the economic and environmental feasibility of the introduction of renewable energies in the island of Pantelleria was assessed adopting an optimization approach. Furthermore, the flexibility provided from the local desalination plant and the domestic water heaters was evaluated. The final demands for electricity, air conditioning, domestic hot water and freshwater were analyzed, and the island was schematized as a multi-carrier energy hub and optimized through a mixed integer linear programming algorithm. Results prove that the renewable energies may provide a strong reduction of operating costs and greenhouse emissions of diesel generators in non-interconnected islands, although the optimal configurations differ according to the objective function of the optimization.

Experimental analysis of a ground source heat pump in a residential installation after two years in operation

Demand Side Management of a pool of air source heat pumps for space heating and domestic hot water production in a residential district

A novel two-stage compression air-source heat pump cycle combining space heating, cooling, and domestic hot water production

Sustainable and energy-efficient domestic hot water systems: A review

Integrated HVAC and DHW production systems for Zero Energy Buildings

Economic feasibility of booster heat pumps in heat pump-based district heating systems

Producing domestic hot water (DHW) with a ground source heat pump (GSHP) is challenging due to the high temperature (HT) of DHW. There are many studies proving the better performance of cascade heat pumps compared to single-stage heat pumps when the difference between the condensing and the evaporation temperature is large. In this system approach study, different GSHP arrangements are described and computationally compared. A two-stage heat pump arrangement is introduced in which water tanks of the heating system are utilized for warming up the DHW in two stages. It is shown that the electricity consumption with this two-stage system is approximately 31% less than with the single-stage heat pump and 12% less than with the cascade system. Further, both low temperature (LT) and HT heat pumps can run alone, which is not common in cascade or other two-stage heat pumps. This is advantageous because the high loads of the space heating and DHW production are not simultaneous. Proper insulation of the DHW and recirculation pipe network is essential, and drying towel rails or other heating coils should be avoided when aiming for a high efficiency. The refrigerants in the calculations are R407C for the LT heat pump and R134a for the HT heat pump. Investment costs are excluded from calculations.

Experimental investigation of gas bubble diameter distribution in a domestic heat pump water heating system

The Lucerne University of Applied Sciences has been analysing and monitoring the low- temperature district heating and cooling network (LTN) “Suurstoffi” since 2012. The analysis showed that heating demand was twice as high as expected. On the other hand, waste heat from free cooling was much lower than expected. The higher heating demand and the lower heat recovery combined resulted in a negative energy balance and hence in an average temperature decrease of the ground storage over the last two years. First of all, a pellet oven was installed as an interim solution in order to supply additional heat to the LTN. Secondly, direct electric heating was used to support the domestic hot water production in order to reduce the energy demand out of the LTN. These temporary measures were only set up until the first part of the planned hybrid solar panels (PVT) were taken into operation in summer 2014. The upcoming data of the monitored summer 2015 will help taking the decision if the temporary measures have to be extended and if additional PVT panels need to be installed. So far, the measured electricity demand to operate the LTN and the connected heat pumps was more than twice as high as expected. This is mainly due to the high electricity demand for temporary electrical heating for domestic hot water, circulation pumps and heat pumps. Thanks to the monitoring, hydraulic shortcoming, which caused the high electrical consumption of the circulation pumps, could be identified. The heat pumps consumed more electricity than planned due to the excess space heating demand and domestic hot water of the consumers. If, in addition to the electricity demand for the heat pumps, the electricity demand of the circulation pumps is taken into account, the overall network efficiency (yearly COP measured = 4.6) is lower than expected (yearly COP planned = 6.8). As a result of the monitoring analysis over the last two years, the following outputs and outcomes could be provided: - The real efficiency of the thermal network has been calculated and benchmarked - Design mistakes have been identified and guidelines for planning have been developed - The energy efficiency has been improved by optimizing the system operation - The accuracy of the monitoring has been improved - The influence of the user on the energy efficiency has been quantified.