Hot Water Usage Research Articles

The performance of an evacuated tube solar hot water system in a domestic house throughout a year in a northern maritime climate (Dublin)

The performance of an evacuated tube solar hot water system, installed on a domestic house (occupied by 2 adults and 3 children) in Dublin, Ireland has been intensely monitored over the period of a year. Instrumentation to measure flows and temperature were installed throughout both the solar circuit and domestic hot water system, in addition to solar radiometers being installed on site to measure both global and diffuse radiation. The overall annual solar system efficiency at the installation angle of 29° to the horizontal was 63%. Heat losses from all aspects of the solar circuit and hot water system have also been quantified. The ongoing hot water usage pattern of the house occupants over the course of the year has been analysed as well as the changing attitudes to the use of hot water since the installation of the new solar system. This has shown some evidence that more hot water tends to be used on days where there has been more direct sunlight. Net present value calculations based on 5years of operation however, have shown that the retrofit of such a system is not currently economically viable, although it has produced a carbon saving of approximately 1.1tonnes CO2eq over its first 5years of operation.

Relationship between building hot water usage and energy and carbon reduction

This article proposes a calculation model for estimating the energy consumption and CO2 emissions resulting from hot water usage and for evaluating the potential for carbon reduction by using a water efficiency strategy. The model revealed a reciprocal relationship between hot water usage in daily life and energy consumption and carbon footprints. From 1990 to 2010 in Taiwan, hot water accounted for approximately 20%–30% of daily water consumption, and the use of hot water indirectly caused an average emission of 6.19 (kg-CO2/m3) and a 1.83% contribution to carbon emissions per capita. The potential influence of hot water usage on the issue of carbon reduction and the importance of strategies for saving water are thus highlighted in this study. Practical application:The proposed calculation model clarified the relationship between hot water usage and carbon emissions. Through the investigation and simulation of domestic hot water usage, the carbon reduction potential of a hot water-savings strategy was validated. This study can make various organizations in both the public and private sectors aware of the importance of building a society based on the concept of water conservation, and various policy-making processes are anticipated to be initiated as a result. Efforts to save hot water could be consolidated to achieve synergy with carbon reduction policies and benefits to building service engineering.

Optimization of photovoltaic–thermal (PVT) based cogeneration system through water replenishment profile

A photovoltaic thermal (PVT) system is a renewable cogeneration system that produces low temperature heat and electricity simultaneously from solar radiation. In water based PVT systems, as the thermal load is served, storage tank is replenished immediately with cold makeup water. However, it is possible to determine an optimal water replenishment profile to optimize the overall configuration of PVT system. In this paper, effects of water replenishment on PVT system sizing are studied. At first, the problem is modeled as a mixed integer non-linear programming problem to analyze the impact of water replenishment on PVT system sizing. Subsequently, the design space approach is used to analyze the significance of water replenishment strategy on the PVT system configuration. Finally, based on analytical derivation, an approximate water replenishment profile is determined and its practical implementation strategies are discussed. Applicability of the proposed methodologies is demonstrated through sizing PVT systems for residential as well as industrial hot water usage patterns. Significant reductions in both collector area (10% for residential example and 7% for industrial example) and storage volume (66% for residential example and 23% for industrial example) are observed.

Geothermal heat pump system assisted by geothermal hot spring

<p><strong>Abstract.</strong> The authors propose a hybrid geothermal heat pump system that could cool buildings in summer and melt snow on the pedestrian sidewalks in winter, utilizing cold mine water and hot spring water. In the proposed system, mine water would be used as cold thermal energy storage, and the heat from the hot spring after its commercial use would be used to melt snow for a certain section of sidewalks. Neither of these sources is viable for direct use application of geothermal resources, however, they become contributing energy factors without producing any greenhouse gases. To assess the feasibility of the proposed system, a series of temperature measurements in the Edgar Mine (Colorado School of Mines' experimental mine) in Idaho Springs, Colorado, were first conducted, and heat/mass transfer analyses of geothermal hot spring water was carried out. The result of the temperature measurements proved that the temperature of Edgar Mine would be low enough to store cold groundwater for use in summer. The heat loss of the hot spring water during its transportation was also calculated, and the heat requirement for snow melt was compared with the heat available from the hot spring water. It was concluded that the heat supply in the proposed usage of hot spring water was insufficient to melt the snow for the entire area that was initially proposed. This feasibility study should serve as an example of "local consumption of locally available energy". If communities start harnessing economically viable local energy in a responsible manner, there will be a foundation upon which to build a sustainable community.</p>

Forecasting Hot Water Consumption in Residential Houses

An increased number of intermittent renewables poses a threat to the system balance. As a result, new tools and concepts, like advanced demand-side management and smart grid technologies, are required for the demand to meet supply. There is a need for higher consumer awareness and automatic response to a shortage or surplus of electricity. The distributed water heater can be considered as one of the most energy-intensive devices, where its energy demand is shiftable in time without influencing the comfort level. Tailored hot water usage predictions and advanced control techniques could enable these devices to supply ancillary energy balancing services. The paper analyses a set of hot water consumption data from residential dwellings. This work is an important foundation for the development of a demand-side management strategy based on hot water consumption forecasting at the level of individual residential houses. Various forecasting models, such as exponential smoothing, seasonal autoregressive integrated moving average, seasonal decomposition and a combination of them, are fitted to test different prediction techniques. These models outperform the chosen benchmark models (mean, naive and seasonal naive) and show better performance measure values. The results suggest that seasonal decomposition of the time series plays the most significant part in the accuracy of forecasting.

단독주택용 태양열/지열 융복합시스템의 태양열 급탕성능 평가

In this study, an analysis was performed on the performance of the solar water heating system with geo-thermal heat pump for a detached house. This system has a flat plate solar collector (<TEX>$8\;m^2$</TEX>) and a 3 RT heat pump. The heat pump acts as an auxiliary heater of the solar water heating system. These systems were installed at four individual houses with the same area of <TEX>$100\;m^2$</TEX>. The monitoring results for one year are as follows. (1) The average daily operating time of the solar system appeared to be 313 minutes in spring (intermediate season), and 135 minutes and 76 minutes in winter and summer respectively. The reason for the short operating time in summer is the high storage temperature due to low water heating load. The high storage temperature is caused by a decrease in collecting efficiency as well as by overheating. (2) The geothermal heat pump as an auxiliary heater mainly operates on days of poor insolation during the winter season. (3) Despite controlling for total house area, hot water consumption varies greatly according to the number of people in the family, hot water usage habits, etc. (4) The yearly solar fraction was 69.8 to 91.5 percent, which exceeds the maximum value of 80% as recommended by ASHRAE. So the solar collector area of <TEX>$8\;m^2$</TEX> appeared to be somewhat greater for the house with an area of <TEX>$100\;m^2$</TEX>. (5) The observed annual efficiency of solar systems was relatively low at 13.5 to 23.6%, which was analyzed to be due to the decrease in thermal efficiency and the overheating caused by a high solar fraction.

Hybrid Roof Panels for Night Cooling and Solar Energy Utilization in Buildings

The aim of this contribution is to evaluate the usability of solar hybrid panels, which were originally optimized for heat load removal from buildings by radiation against the night sky, for water preheating. First we created a surrogate model based on CFD simulations defining performance of the panel dependent on changing boundary conditions. This model was then implemented to the water heating model created in TRNSYS software. Estimated hot water usage would suffice for operation of 2 restaurant facilities in a building of our interest. Subsequent simulations were carried out using reference year climate data for Brno (Central Europe). Results demonstrated that in the given conditions, the average annual efficiency of solar energy usage is 55%. The results also showed that the system is able to cover approximately 7% of the heat demand for water heating.

Water consumption characteristics at a sustainable residential development with rainwater-sourced hot water supply

The use of water-efficient appliances and inclusion of alternative water sources in urban residential developments is becoming increasingly necessary to meet the growing demands on conventional urban water supplies. As an initiative commissioned by the South Australian State Government in 2009, Lochiel Park is a recent model designed to embrace sustainable planning principles and technologies in a domestic context. An extensive post-occupancy monitoring program of actual residential water and energy usage was conducted. The study aimed at analysing and quantifying the water consumption at 59 houses through real-time monitored data collected over 3 years between 2010 and 2013, incorporating the monitored usage of mains water, collected rainwater and hot water usage. The analysis shows that the annual average total water consumption per household at Lochiel Park is significantly lower than both the Adelaide and national averages by about 24% and 16% respectively, while average mains water consumption is lower by 36% and 29% respectively. Rainwater contributes 6–10% of the total water use in summer and up to 26% in winter, with an average annual contribution of around 14%. A significant part of the saving is attributed to the increased minimum rainwater tank capacity from the 1 kL specified in the Building Code of Australia to 1.5 kL, and feeding rainwater into the hot water supply in a climate where rainfall occurs in winter. Although a reduced hot water demand is also prompted by having efficient fixtures and rainwater supply depends on climate, rainwater fed into hot water supply saves 40% of hot water consumption annually. Greater rainwater utilization in hot water is possible if rainwater tank sizing and a greater roof catchment area can match household winter hot water demand, rather than having a single minimum requirement across all households as in the current regulation. The study provides an understanding of the performance of alternative urban water systems. The outcomes verify the effectiveness of the Water Sensitive Urban Design (WSUD) features implemented and will be useful for future strategic planning and design initiatives for implementation of similar developments on a larger scale.

Evaluation of solar hot water heating system applications to high-rise multi-family housing complex based on three years of system operation

This study evaluated three-year operation of solar hot water heating system installed in multi-family housing complex with 1179 households in 14 units. At first, since the size of systems for multi-families are large, position of the building services room and collector installation becomes a significant matter. In order to resolve this, three building services rooms for three or four units of households were planned and the solar collectors were integrated directly on the roof facing South at 22° degrees to the horizontal. The accumulated heat gain from three-year operation was 52% of the design baseline (4069GJ/year). The reason for this could be a low altitude angle of collectors from the architectural design. Moreover, hot water usage and breakdowns of the system were evaluated using detailed analyses of operation data for three years by considering seasonal factors. These results are expected to give valuable feedback for the future design and wide use of the systems, as well as update the design baseline. Lastly, compared to a conventional boiler(δ=85%), the system produced a positive environmental effect equivalent to a reduction in oil use of 71,907L/year, and reduced carbon emissions equivalent to 50.8 TC and 186.3 TCO2 the pay-back period for the system was expanded 5 years.

TRNSYS Modeling of a Linear Fresnel Concentrating Collector for Solar Cooling and Hot Water Applications

In this paper, simulation of a linear Fresnel rooftop mounted concentrating solar collector is presented. The system is modeled with the transient system (trnsys) simulation program using the typical meteorological year file containing the weather parameters of four different cities in Australia. Computational fluid dynamics (CFD) was used to determine the heat transfer mechanism in the microconcentrating (MCT) collector. Ray trace simulations using soltrace (NREL) were used to determine optical efficiency. Heat loss characteristics determined from CFD simulation were utilized in trnsys to assess the annual performance of the solar cooling system using an MCT collector. The effect of the different loads on the system performance was investigated, and from trnsys simulations, we found that the MCT collector achieves a minimum 60% energy saving for both domestic hot water usage and high temperature solar cooling and hot water applications.

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 5-Analysis of Energy Consumption and Efficiency Performance on CO_2 Heat Pump Water Heater based on the Simulation

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 5-Analysis of Energy Consumption and Efficiency Performance on CO_2 Heat Pump Water Heater based on the Simulation

태양열 콤비시스템의 축열조에 적용되는 분배기의 효과

Return piping is used in a solar combi-system for heating and hot water supply. When the temperature of the lower side of a storage tank is low due to hot water usage, the returned hot water after heating is mixed with the lower side cold water of the tank, and the useful energy is reduced. We studied the degree of thermal stratification in the tank, using either a diffuser or a manifold to prevent mixing. Using the diffuser, mixing starts from the bottom of the storage tank. On the other hand, the manifold has the marked effect of preventing mixing. As a result of experiments with changing the diameter and number of holes in the manifold, the optimum condition is 8.5 mm diameter and 96 holes, under the condition of 0.3 lpm.

Real-Time Scheduling of Residential Appliances via Conditional Risk-at-Value

This paper investigates the real-time scheduling of residential appliances in the home energy management system (HEMS), including electric water heater (EWH), air conditioner (AC), clothes dryer (CD), electric vehicle (EV), photovoltaic cell (PV) and battery. A demand response (DR) mechanism is proposed to stimulate the household to participate in the DR services. The conditional value-at-risk (CVaR) is applied to make a trade-off between the expected costs and the risk of exposure to uncertainties of the electricity price and other factors. Fuzzy logic controller is utilized to determine the output power of the battery, and two sets of rules are designed to adjust the charging and discharging operations of the battery according to the DR request from the grid. Stochastic aspects of the electricity price, outdoor temperature, hot water usage, PV generation, and loads are considered. Simulation results show that the proposed DR mechanism can decrease the cost of the household considerably, and the proposed real-time scheduling algorithm can optimize the operation of appliances close to the ideal deterministic results, even when the gap between the forecast electricity price and the real price is large.

Solar water heater contribution to energy savings in higher education institutions: Impact analysis

This paper focuses on the impact of Solar Water Heaters (SWH) at a higher institution of learning. An energy audit was conducted for the evaluation of the energy conservation measure: energy conoduction Energy is a key element in the development of any country or institution; as a result any shortage in energy will have a serious effect on the economy and social aspect of such country or institution. South Africa has, in recent years, experienced high economic growth as well as a rapid expansion in the elsumption analysis, correlation of consumption with weather; financial criteria, payback period and needed solar heater system (SWH) to determine the energy that may be termed as wastage or can be saved. The method of investigation includes assessment of the hot water usage within the institution campus and residencies, analysis of bills, metering and development of a software model for the analysis of energy use, system needed and environmental variables. This renewable measure (SWH) showed a high potential of energy and financial savings for higher education institutions especially those with residences.

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 4-Development of the Calculation Method for Energy Consumption and Efficiency Performance

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 4-Development of the Calculation Method for Energy Consumption and Efficiency Performance

English

In ENT OPD indirect laryngoscopy is a routine procedure to examine larynx and hypopharynx. To prevent the fogging of the mirror authors used hydrogen peroxide 0.75% w/v solution which is safe and cost effective when compared to other methods to prevent fogging. KEYWORDS: Hydrogen peroxide (H2 O2), Indirect laryngoscopy (IDL), Defogging INTRODUCTION: Indirect laryngoscopy which was invented by Manuel Garcia, in 1854 and further devoiced by Dr. Johann Czermak in1857 is a routine ENT OPD procedure to visualize larynx and pharynx which is relatively simple. (1-2). When compared to fiber optic system (Rigid telescopes) the resolution of the IDL is superior to that of endoscopic examination. Apart from naked flame and hot water and using savlon this is preferred method which eventually may lead to burning of oral mucous membrane and bad taste sensation. MATERIAL AND METHODS: Dilute hydrogen peroxide solution (0.75%w/v) is used as a defogging agent on sterilized indirect laryngeal mirrors in all cases, where indirect laryngoscopic examination is required. The same solution is also used in different other occasions like few dental procedures and as a mouth wash in post tonsillectomy patients (1.5% w/v). The solution is dropped over the mirror surface and an excess is wiped off by using a Goss piece. This way a thin film of solution is formed over the surface of the mirror the patient is examined with this mirror and no fogging occurred during the procedure. The mirror is tested by emersion into the hydrogen peroxide solution 3% w/v for 24hrs and there is no deterioration in the quality of the mirror. RESULTS: For the last two years this method of defogging the indirect laryngoscopy mirror has shown no untoward incidence in our ENT OPD. Warming the mirror with spirit lamp has caused some burning incidences previously and patients become uncooperative. So this method is bypassed. Using savlon, patients complained of bad taste in the mouth. Hydrogen peroxide solution as such acts as antiseptic and is patient friendly and safe. DISCUSSION: Since the body temperature is higher than that of the mirror, when IDL mirror is introduced in the oral cavity, as soon as the patient expires there will be condensation of water vapor over the mirror. This leads to formation of fogging of the mirror. This leads to blurring of the image, so prevention of fogging becomes necessary. To do so, many centers use spirit lamp flame to warm the mirror surface. But the fact is the spirit lamp caused untoward incidences in over 100 ENT cases in UK over the years, such as injuries by the patients and staff being burnt by naked flame(3) and injuries by overheating of the mirrors. When the mirror is heated by the flame of spirit lamp,patients get worried and apprehensive. They think that it may burn oral cavity and throat. Usage of hot water is not suitable as the risk of scalding is much greater and repeated usage of same water causes cross infections. (Few centers in UK use baby bottle warmers to keep the

The Theoretical Modelling and Optimization of a 10 KWP Photovoltaic Thermal System for a Student Hostel in Singapore

Current commercial photovoltaic (PV) conversion efficiency (flat plate modules) is about 6--20%, depending on the materials used for the module construction. Since only a small fraction (<10%) of the incident solar energy is reflected and/or transmitted, a large fraction of the solar radiation is converted into heat. If this heat can be harvested as well, the overall energy efficiency of such an integrated photovoltaic thermal (PVT) hybrid system will be greatly improved. At the same time, pumping water through the PV modules will cool (if Twater < Tmodule) the solar cells and improve their electricity production efficiency. This article describes the design and numerical simulation of a PVT system for producing electricity and hot water in a student hostel in Singapore. The nominal electrical power output is 10 kWp (kilowatt peak). Thermal models were developed based on basic energy balance equations and average climatic conditions for Singapore over a typical year were used. A survey of the hot water usage pattern over a typical week was carried out and used in the simulation. The optimum mass flow rate in the collectors is found to be 0.039 kg/(s m2) and the optimum storage tank capacity for hot water is 2500 kg for a showering load of around 6000 kg/day. The average thermal and electrical efficiency of the system are 43% and 12%, respectively. The requirement of auxiliary electric energy for water heating is predicted to be reduced by 94%.

Hotel heat pump hot water systems: impact assessment and analytic hierarchy process

Purpose – Water heating is one of the major energy‐consuming operations in the lodging sector. The purpose of the current study is to estimate the energy consumed and emission associated with hot water usage, to predict the energy cost required under different hot water systems in hotels; and to create a model for the decision‐making criteria in selecting hot water systems.Design/methodology/approach – A total of 24 hotels, which use heat pumps as their main water heating systems, were investigated. A tailor‐made model for estimating the energy requirement of the water heating system was employed. Comparative studies on the energy consumption and energy costs of various types of water heating systems, including heat pumps, diesel boilers, gas boilers, and electric boilers, were conducted. Moreover, an analytic hierarchy process was used to analyze hoteliers' and lenders' selection criteria for water heating facilities.Findings – The energy output for water heating by heat pumps was estimated at 15 GW in t...

Energy performance optimization for Army installations

Buildings contribute to a large fraction of energy usage worldwide. In the United States alone, buildings consume about 40% of total energy expenditure, including 71% of electricity and 54% of natural gas. 1 The Army alone spends more than US $1 billion for building-related energy expenses. The 2005 Energy Policy Act 2 requires that Federal facilities be built to achieve at least a 30% energy savings over the 2004 International Energy Code or ASHRAE Standard 90.1-2004, as appropriate, and that energy efficient designs must be life-cycle cost effective. According to the Energy Independence and Security Act (EISA 2007), 3 new buildings and buildings undergoing major renovations shall be designed to reduce consumption of energy generated off-site or on-site using fossil fuels, as compared with such energy consumption by a similar building in fiscal year 2003 (FY03) as measured by Commercial Buildings Energy Consumption Survey (CBECS) or Residential Energy Consumption Survey (RECS) data from the Energy Information Agency, by 55% in 2010, 80% by 2020, and 100% by 2030. Current US research efforts focus on renewable energy sources and single-building energy efficiency, and pay little attention to integration and minimization of energy use in building communities, i.e. Army installations and university campuses. There is no over arching ‘power delivery/energy storage/demand’ architecture and methodology to accomplish this. This article describes the Net Zero fossil fuel-based energy optimization process and illustrates it with an example based on the results of study conducted for a cluster of buildings at Fort Irwin, CA. Application of the energy optimization process to new construction and major retrofit project shows17–20 that use of high performance building envelope (improved insulation and air tightness), advanced lighting strategies, and efficient HVAC systems results in significant energy savings (site and source) in Army buildings in all climates. When buildings built or retrofitted with a high performance building envelope, using advanced lighting systems and highly efficient ‘low exergy’ HVAC systems, reach a theoretical energy use minimum, the largest percentage of the remaining energy use in the building will be related to its ‘mission’: lighting, plug loads, and domestic hot water usage. Additional savings may be achieved with measures related to improved efficiency of power generation supplied to the building (co- and tri-generation) and use of energy supplied from renewable energy sources. The integrated energy solution recommended here demonstrates that vastly improved energy efficiency and GHG reduction are feasible in the context of a normal scale development using proven approaches from the USA and elsewhere. Moreover, the optimization process can be applied to new construction and major renovation of buildings and building clusters projects developed for low energy communities.

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 3-Development of the Experimental Mode on Hot Water Loads with Reheating Bathwater

Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 3-Development of the Experimental Mode on Hot Water Loads with Reheating Bathwater