High performance in low-flow solar domestic hot water systems

Dayan, Myrna

doi:10.2172/578464

Cited by 15 publications

(11 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, the requirement on the size of components in low flow systems is reduced. This is the case of the heat exchanger capacity, pipe diameter, pump sizes and their energy consumption [2,12,50]. The annual solar fraction result is in accordance with previous studies for the same kind of standard SWH systems with comparable collector area, storage type, storage volume, mean domestic hot water load and weather conditions [18,53].…”

Section: Mass Flow Ratesupporting

confidence: 88%

“…One of the biggest obstacles to the economic profitability of domestic solar water heating (SWH) systems is the investment cost [1][2][3]. The installation cost of forced circulation systems used in cold climates can represent up to 50% of the total investment cost depending on the size and type of system [4].…”

Section: Introductionmentioning

confidence: 99%

“…Such dependence on the heat exchanger pressure drop and tank characteristics limits how the retrofit is carried out, where the heat exchanger should be placed and which storage tanks can be used [12]. Moreover, when properly designed, forced circulation systems can significantly achieve higher performances compared with natural convection driven systems [2,[12][13][14]. This is mainly explained by the increase in energy transfer rate at a low energy driving cost.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, low energy pumps are now available at a lower cost. The disadvantages of forced circulating systems are stated to be a higher degree of complexity and the demand for electricity to run the pumps and controls [2,12].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Retrofitting Domestic Hot Water Heaters for Solar Water Heating Systems in Single-Family Houses in a Cold Climate: A Theoretical Analysis

Bernardo

Davidsson

Karlsson³

2012

Energies

View full text Add to dashboard Cite

Abstract:One of the biggest obstacles to economic profitability of solar water heating systems is the investment cost. Retrofitting existing domestic hot water heaters when a new solar hot water system is installed can reduce both the installation and material costs. In this study, retrofitting existing water heaters for solar water heating systems in Swedish single-family houses was theoretically investigated using the TRNSYS software. Four simulation models using forced circulation flow with different system configurations and control strategies were simulated and analysed in the study. A comparison with a standard solar thermal system was also presented based on the annual solar fraction. The simulation results indicate that the retrofitting configuration achieving the highest annual performance consists of a system where the existing tank is used as storage for the solar heat and a smaller tank with a heater is added in series to make sure that the required outlet temperature can be met. An external heat exchanger is used between the collector circuit and the existing tank. For this retrofitted system an annual solar fraction of 50.5% was achieved. A conventional solar thermal system using a standard solar tank achieves a comparable performance for the same total storage volume, collector area and reference conditions.

show abstract

Section: Mass Flow Ratesupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Retrofitting Domestic Hot Water Heaters for Solar Water Heating Systems in Single-Family Houses in a Cold Climate: A Theoretical Analysis

Bernardo

Davidsson

Karlsson³

2012

Energies

View full text Add to dashboard Cite

show abstract

“…Since both a new solar heating store and a new docking unit are added, the space requirements are increased and the cost reductions limited. Furthermore, when properly designed, forced circulation systems can significantly achieve higher performances compared with natural convection driven systems [14,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Retrofitting Conventional Electric Domestic Hot Water Heaters to Solar Water Heating Systems in Single-Family Houses—Model Validation and Optimization

Bernardo

2013

Energies

View full text Add to dashboard Cite

System cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly reduce both material and installation costs. In this study, the TRNSYS simulation models of the retrofitting solar thermal system were validated against measurements. Results show that the validated models are in good agreement with measurements. On an annual basis a deviation of 2.5% out of 1099 kWh was obtained between the auxiliary energy from results and from the simulation model for a complete system. Using the validated model a system optimization was carried out with respect to control strategies for auxiliary heating, heat losses and volume of auxiliary storage. A sensitivity analysis was carried out regarding different volumes of retrofitted hot water boiler, DHW profiles and climates. It was estimated that, with adequate improvements, extended annual solar fractions of 60%, 78% and 81% can be achieved for Lund (Sweden), Lisbon (Portugal) and Lusaka (Zambia), respectively. The correspondent collector area was 6, 4 and 3 m 2 , respectively. The studied retrofitted system achieves a comparable performance with conventional solar thermal systems with the potential to reduce the investment cost.

show abstract

Performance testing of thermal and photovoltaic thermal solar collectors

Allan

Dehouche

Stankovic³

et al. 2015

Energy Science & Engineering

View full text Add to dashboard Cite

This work details a methodology to characterize the performance of solar thermal and photovoltaic thermal (PVT) collectors using an indoor solar simulator. In this study, several cases have been compared to show that the methodology can be used to extract fundamental performance characteristics from a solar collector. In the first case, a serpentine collector was compared against a header riser collector using the same mass flow rate. It was found that the header riser was less efficient, with a 34% increase in the overall loss coefficient. The experimental results were compared with commonly used empirical models and showed a close agreement. In the second case, the impact on performance of using a polycarbonate cover is presented. The results show that the optical efficiency of the collector is reduced by 12% when using a cover; however, because the loss coefficient is reduced by 53%, the covered collector performs better when there is a large temperature difference between the absorber and the ambient. The third case investigates the combined performance of a PVT collector, that produces both heat and electricity from a single device. By placing photovoltaic (PV) laminates on top of the serpentine absorber, the thermal efficiency is reduced by 15%. When electricity is generated by laminates, the thermal efficiency is reduced by a further 3.5%; this drop in thermal efficiency is a result of the incident radiation producing electricity before reaching the thermal absorber. The combined efficiency of the PVT collectors was compared at controlled inlet temperatures. The serpentine design had the highest combined efficiency of 61% with 8% electricity at the lowest inlet temperature (21°C). The dominant form of loss in the PVT system is temperature driven; as the thermal efficiency decreases, electricity generation makes up a larger percentage of the combined output. This study highlights the potential for manufacturers of bespoke thermal absorbers and PV devices to combine their products into a single PVT device that could achieve improved efficiency over a given roof area. 311

show abstract

High performance in low-flow solar domestic hot water systems

Cited by 15 publications

References 10 publications

Retrofitting Domestic Hot Water Heaters for Solar Water Heating Systems in Single-Family Houses in a Cold Climate: A Theoretical Analysis

Retrofitting Domestic Hot Water Heaters for Solar Water Heating Systems in Single-Family Houses in a Cold Climate: A Theoretical Analysis

Retrofitting Conventional Electric Domestic Hot Water Heaters to Solar Water Heating Systems in Single-Family Houses—Model Validation and Optimization

Performance testing of thermal and photovoltaic thermal solar collectors

Contact Info

Product

Resources

About