A review of water heating technologies: An application to the South African context

Hohne, P.A.; Kusakana, K.; Numbi, B.P.

doi:10.1016/j.egyr.2018.10.013

Cited by 106 publications

(45 citation statements)

References 86 publications

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“…Water heating is a major source of energy consumption in a residential building and may account between 11% in the USA up to 32% in South Africa, of the total energy consumption [1,2]. There are various alternatives for this basic purpose and they include: electrical heating, solar panels, oil fired boilers, biomass and heat pumps.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Plate Orifice in the Pre-Mixing of Gas-Powered Water Heaters

Magalhães

Ferreira

Teixeira

et al. 2020

The First World Energies Forum—Current and Future Energy Issues

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Amongst the various alternatives for hot water production for domestic use, instantaneous heaters are still widely used in many markets such as the Portuguese market. In this system, a gas boiler converts the chemical energy of the gas (Liquefied Petroleum Gas, Natural Gas) to a water stream, as it is used. The complexity of such devices ranges from those with a natural convection to those with full pre-mixing of the air-fuel. The tightening of the legislation targeting these appliances is promoting an increase in efficiency, pollutant emission reduction and an increase in the safety features. The purpose of this work was to test the thermal performance of a water heater prototype with 22 kW of nominal heat output, running on Propane. Changes were made to the plate with orifices that limit the air supply to the burner flutes, where the pre-mixture with the fuel is partially made. Four different plates with different orifice diameters were built and tested in real case scenarios, taking into special consideration the pollutant emission and the fuel consumption verified. From the results, it was concluded that the best configuration in terms of efficiency is the original one, followed by the “−0.5 mm” and “−1 mm” plates. On the other hand, the best plate in terms of CO emission was the “−1 mm” plate. Concerning the plates with larger diameters to the manufacturer’s original configuration, flame instability was verified as a result of the greater primary airflow. Under the same test conditions, it was noted that the introduction of a nozzle into the fan inlet led to the suction of a larger amount of air. Finally, it was also concluded that the reduction in the orifice diameters of the plates reduces the split of primary air, resulting in an increased pressure drop in the flutes and in the overall pressure drop of the system.

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Section: Introductionmentioning

confidence: 99%

“…The instantaneous route has some advantages, namely: hot water is always available, there are no standby losses, and the compactness and robustness of the device [2]. The investment cost per kW compares favorably with other alternatives.…”

Section: Introductionmentioning

confidence: 99%

Influence of Plate Orifice in the Pre-Mixing of Gas-Powered Water Heaters

Magalhães

Ferreira

Teixeira

et al. 2020

The First World Energies Forum—Current and Future Energy Issues

View full text Add to dashboard Cite

show abstract

“…A large contributor to domestic electrical energy usage in developing countries is water heating (Hohne et al, 2019). In South Africa, for example, the residential sector uses an estimated 17 % of the total electricity generated, with domestic water heaters being responsible for a combined 38.5 GWh/day (Forlee, 1998;Beute and Delport, 2006;Eskom, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The relevant literature and major remaining challenges for energy saving through scheduled control of storage-based water heaters are listed in Table 1 and summarised in the following section. In developing countries, where the user typically pays a time-independent flat fee per kWh, and not a tariff based on time-of-use or congestion, poorer users resort to schedule control simply to reduce their monthly bill, and possibly their environmental footprint (Nel et al, 2016b;Hohne et al, 2019), and not to shift peaks or to avoid congestion charges. In this situation it is the user who bears the burden of the increased energy usage that may result from any demand management schemes (Roux et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

How much energy can optimal control of domestic water heating save?

Booysen

Engelbrecht

Ritchie

et al. 2019

Energy for Sustainable Development

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Scheduled control of domestic electric water heaters, designed to cut energy use while minimising the impact on users' comfort and convenience, has been fairly common for some time in a number of countries. The aim is usually load-shifting (by heating water at off-peak times) and/or maximising time-of-use pricing benefits for users. The scheduling tends not to be linked to actual hot water usage and depends largely on stored thermal energy. Heat losses therefore tend to be greater than if the heater ran without a break. The effect of such a control strategy is thus to worsen the energy loss and in most cases increase greenhouse gas emissions. Many developing countries have flat-pricing (no time-of-use incentives) and rely heavily on energy from fossil fuels, making these considerations even more pressing. We explore three strategies for optimal control of domestic water heating that do not use thermostat control: matching the delivery temperature in the hot water, matching the energy delivered in the hot water, and a variation of the second strategy which provides for Legionella sterilisation. For each of these strategies we examine the energy used in heating, the energy delivered at the tank outlet, and issues of convenience to the user. The study differs from most previous work in that it uses real daily hot-water usage profiles, ensures like-for-like comparison in delivered energy at the point of use, and includes a daily Legionella avoidance strategy. We tackled this as an optimal control problem using dynamic programming. Our results demonstrate a median energy saving of between 8% and 18% for the three strategies. Even more savings would be realised if intended and unintended usage events are correctly classified, and the optimal control only plans for intended usage events.

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“…Direct control provides the benefit of being able to reduce the strain on the grid during high demand periods, but does not take the comfort of the user into account. Combining the benefits of EWH management and load-matched solar PV generation in a school environment can potentially provide large reductions in monthly demand charges by reducing a school's peak power demand while maintaining user comfort (Hohne et al, 2019). This will also provide the opportunity to divert excess generated solar energy to be stored in the EWH, reducing the potential grid load used by the EWHs and maximising all three control objectives.…”

Section: Introductionmentioning

confidence: 99%

Combining grid-tied PV and intelligent water heater control to reduce the energy costs at schools in South Africa

Gerber

Rix

Booysen

2019

Energy for Sustainable Development

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South Africa's escalating electricity rates are increasingly diverting educational resources to utility bills. Recent advances in solar PV affordability, the advent of the smartgrid and the capacitive nature of water heaters could be combined to enable new methods for electricity cost and efficiency management without affecting user comfort. Control methods that combine excess PV energy dumping and real-time temperaturebased prioritised scheduling were compared with the normally-employed thermostat control. In addition, the performance of an energy-optimising approach is compared with a peak demand optimising approach. The results show that peak demand limiting with a two-temperature thermostat provided the highest cost saving with a 30% reduction of the school's electricity cost and only a 0.2 percentage point reduction in the number of warm water events.

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A review of water heating technologies: An application to the South African context

Cited by 106 publications

References 86 publications

Influence of Plate Orifice in the Pre-Mixing of Gas-Powered Water Heaters

Influence of Plate Orifice in the Pre-Mixing of Gas-Powered Water Heaters

How much energy can optimal control of domestic water heating save?

Combining grid-tied PV and intelligent water heater control to reduce the energy costs at schools in South Africa

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