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A comprehensive coupled thermal-optical model is developed in MATLAB to predict the performance of a flat plate collector (FPC) and matching its hot water supply with demand of a typical household. The developed model is validated with outdoor and indoor experimental results. The validated model is extended to weather data of a semi-arid climatic condition of Lahore, Pakistan. Monthly and yearly optimum tilt angle is found by selecting its value where FPC gives maximum efficiency throughout the day. The thermal performance of the FPC is evaluated at one clear day of each month for a fixed flow rate to determine its outlet temperature at maximum efficiency. A variable flow rate is also determined for maintaining a fixed outlet temperature. Furthermore, an analysis of demand and supply is carried out. The analysis shows that the efficiency of the FPC remains between 70% and 77% for six hours (09:30 and 15:30) in all months for a fixed flow rate. The flow rate variations in the range of 0.01 kg/s to 0.1 kg/s can maintain a fixed outlet temperature of 50 °C. It is also found that the FPC with a variable flow rate can meet the demand of a typical household by employing 8 collectors connected in parallel.

The energy demand for supplying Domestic Hot Water (DHW) has an important share in the overall thermal energy consumption of commercial buildings. The aim of this paper is to analyze the performance of DHW production in commercial public service, i.e., educational buildings, to subsequently identify frequent inherent shortcomings of centralised DHW installations and to provide measures for optimization or economically more viable solutions. Several buildings of the University of Natural Resources and Life Sciences in Vienna have been investigated in terms of DHW consumption and performance of the installed centralised systems. Referring to the investigated university buildings, it can be stated, that in cases of low to medium consumption figures, typical centralized DHW installations with a hot water circulation pipework achieve only poor efficiencies in the range of 2–12%. As for one particular centralized DHW system in operation, focusing on demand controlled DHW supply through adapted flow control, e.g., reducing the runtime of the circulating pumps at specific time intervals, and, if applicable and feasible, decreasing hot water flow- and storage capacities can reduce annual energy consumption for DHW by 15–25% and improve the overall system efficiency significantly as could be evaluated in a detailed case study. A seemingly economical yet ecologically controversial option for improving centralised DHW systems is the partial or complete conversion to electric point-of-use water heaters. This reduces thermal energy losses almost completely, hereby significantly increasing the efficiency of a DHW supply system. Nevertheless, existing hot water supply systems, energized by district heating, usually consume less primary energy and most likely generate fewer CO2 emissions compared to electric DHW heaters.

In this study, the usefulness of adding a solar system to a domestic hot water supply system (boiler) was investigated. The amount of hot water consumption was determined taking into account hot water usage on workdays and weekends. Considering the amount of global horizontal irradiation 2328.2 kwh m 2 . y e a r for southwest region (Wadi Al-Dawasir) in Saudi Arabia and using transient analysis, the heat gain in collectors was specified at the optimal tilt. The results showed that by adding a solar system (which used water at 30 kg hr ) the boiler power usage reduced by 21,389 kWh per year. Based on numerical calculations, the higher flow rates in collector (60 and 90 kg hr ), the lower energy saving (19550 and 18663 kWh year ). Dispersing nanoparticles of Pentaethylene Glycol-Treated Graphene Nanoplatelets (GNPs + PEG) into water at 0.025–0.1 vol% led to a superior energy-saving. At 30 kg hr , owing to using GNPs + PEG/water at 0.025 vol%, energy saving improved by 1080 kWh year (from 21,389 to 22,469 kWh year ). Loading more nanoparticles resulted to higher energy-saving so that at 0.1 vol%, it was 23,376 kWh year . Under the best case conditions and owing to using solar system, the boiler energy usage reduced by 26.8% (for water) and 29.3% (for GNPs + PEG/water 0.1 vol%).

In our search for a better socioeconomic path for water heater usage in China, we studied and compared the annual dynamic thermal performance of solar water heaters (SWHs) in the Jiangsu province. Experiments are conducted in two cities within Jiangsu—Nanjing and Lianyungang—spanning two climate zones. The results show that SWHs have good thermal performance in Jiangsu. The SWHs in Lianyungang show better thermal performance than that in Nanjing, because they receive greater solar radiant energy. Also, from a thermal perspective, vacuum tube solar water heaters (VTSWHs) perform better throughout the year than flat-plate solar water heaters (FPSWHs). Meanwhile, taking socioeconomics into account, gas-assisted flat-plate solar water heaters (GA-VTSWHs) have better performance compared to other types of water heaters. Based on these results, the implications for developing and applying SWHs are derived. This study can be used to optimize operation of the household hot water supply system and use it more efficiently.

Occupants’ behavior and their interaction with home appliances are crucial for assessing building energy consumption. This study proposes a new methodology for monitoring the energy consumed in building end-use loads to build an advisory system. The built system alerts occupants to take certain measures (prioritized recommendations) to reduce energy consumption of end-use loads. The quantification of potential savings is also provided upon following said measures. The proposed methodology is also capable of evaluating the energy savings performed by the occupants. The system works based on the analysis of historical data generated by occupants using data mining techniques to output highly feasible recommendations. For demonstration purposes, the methodology was tested on the real dataset of a building in Japan. The dataset includes detailed energy consumption of end-use loads, categorized as hot water supply, lighting, kitchen, refrigerator, entertainment & information, housework & sanitary, and others. Results suggest that the developed models are accurate, and that it is possible to save up to 21% of total energy consumption by only changing occupants’ energy use habits.

Energy saving and environmental protection have become the core development concept of China construction industry. There are still a large number of old urban buildings in Beijing, whose energy consumption far exceeds the current building energy efficiency standards. The energy-saving renovation of these old buildings has been becoming the focus and difficulty of urban building energy-saving. In this paper, a calculation model based on the TNM Decree is proposed to calculate and analyze the energy consumption of heating and domestic hot water supply in winter before and after the renovation of old urban buildings in Beijing. The calculation results show that the thermal insulation performance of building envelope is a key factor affecting the energy consumption of old urban buildings. After the renovation, the energy-saving rate of the old urban buildings completed between 1978 and 1985 can reach 65.53%. The energy-saving rate of the buildings completed between 1986 and 1995 and that between 1996 and 2005 can reach 55.04% and 32.79%, respectively.

openaire: EC/H2020/856602/EU//FINEST Twins In this paper, the demand response of district heating for swimming pools and pool space air is proposed and applied in a swimming hall in Finland. Swimming halls have significant heat demands e.g., domestic hot water supply, space heating and pool water heating, and thus have much large heat storage capacity for the realization of district-heat based demand response. A dynamic building simulation tool IDA ICE was used to simulate whole swimming hall including pools and HVAC systems. In addition, a rule-based demand response algorithm which utilized dynamic district heat price was proposed and applied in the district heating control of the studied swimming hall. The results show that the large storing capacity of pool water promises the large amount of charged and discharged heat energy, and ensure the application of demand response of district heating in swimming hall. The application of demand response of district heating can increase the average pool water temperature from the normal setpoint of 26.5 °C to27.3 °C. In addition, demand-response district heating control for the swimming pool water and pool space air decreases the total district heat costs of the swimming hall by 1.1%. During the repayment periods of 7 and 15 years, the energy cost savings and maximum cost of profitable investment for the demand response control are between 10 000 € and 20 000 €.

Solar energy as one of the renewable and abundant energy resources, was often harvested by flat plate solar collectors (FPCs) for heating and hot water supply. However, the FPC suffered significant heat losses and overheating problems due to poor design or sometimes extremely adverse environmental conditions, which further limited its application and operation. In this study, an automatic movable cover plate (MCP) was applied to the v-corrugated flat-plate solar collector (VFPC), a dynamic heat transfer model was developed, and a comparative experiment was conducted to analyze the effects of MCP on heat loss and overheating performance. The influence of environmental and operating parameters was analyzed under three typical operation conditions: (I) heat collection in summer, (II) overheating in summer and (III) heat collection in winter. For Condition I, the MCP could decrease the temperature fluctuation of heat transfer fluid from 18.9 to 5.7 ℃ in cloudy weather. For Condition II, the MCP with high absorptivity and low emissivity value could reduce the collector “stagnation” temperature to a lower value. For Condition III, the MCP could reduce the total heat loss to 62.8% and decrease the heat demand of reverse circulation by 4.5 MJ in 48 h. The FPCs incorporated with novel MCP showed excellent performance on synergistically reducing heat loss and preventing overheating problems, demonstrating the advantages of applying flat plate collectors in more wide temperature ranges and variable environments.

A photovoltaic/thermal (PV/T) direct-driven refrigeration/heating system was proposed in this paper. This system had the functions of off-grid refrigeration and hot water supply without using batteries. The solar refrigeration efficiency could also be improved by means of PV cell cooling in PV/T modules and compressor speed controlling. In this paper, performance of this system was investigated by experiments and numerical simulations. The influences of the total capacity of PV cells and water temperature in the ice storage tank were also studied. When the number of PV cells increased, the daily cooling capacity per cell increased first, then decreased. This revealed that the capacities of the compressor and PV cells should be designed to improve the PV utilization efficiency. Total cooling capacity of the system increased with the increase of initial water temperature in the ice storage tank. This revealed that high initial water temperature was benefit for system cooling capacity.

There is growing interest in using alternative water sources such as rainwater harvesting and treatment systems to supplement traditional sources and secure a stable supply. For such systems, it is important to ensure adequate water quality, as microbial contamination can be a risk factor in rainwater. The primary objective of this study was to provide proof-of-concept for the microbial treatment capacity of a residential scale rain-to-hot-water treatment system to be installed in Melbourne, Australia. The system consists of a filtration, UV and heat-pump hot water unit, and disinfects roofwater prior to use of the hot water for bath, shower and laundry. The system's efficiency was evaluated using long-term challenge tests investigating the full system and each of the separate components. The microbial treatment performance was assessed based on the systems' ability to treat high levels of E. coli, E. faecalis, Campylobacter, Salmonella and MS2 phage under challenging conditions; with varying flow rates (10-40 L/min) and microbe concentrations (104-105unit/L), and in scenarios of a power outage. Over a compressed year of operation, the full rain-to-hot-water treatment system was extremely efficient at reducing concentrations of E. coli, E. faecalis, Campylobacter, Salmonella and FRNA phages, with log reductions ranging from the lowest average of 2.1log reductions for Salmonella to a maximum of >5.1log for E. coli. Most of the treatment was provided by the UV system, and any remaining microbes present after this point were deactivated by the heat-pump system (provided that the water was given enough time to warm up). Additional modelling work showed that UV intensity, UV transmissivity and contact time (for the UV system) and temperature (for the heat-pump hot water system) could be used as parameters to predict microbial treatment performance of the system, indicating that these easily-measurable parameters could assist with ongoing operation optimisation and maintenance of such systems.

In this study, comparison between combined and cascade CO2/R134a heat pump systems were investigated theoretically. The characteristics of the R134a and CO2 cycles in both combined and cascade systems were studied under different working conditions. The evaporation temperature in the R134a cycle and the discharge pressure in the CO2 cycle were first evaluated in the combined and cascade systems. Results showed that the change of the R134a evaporation temperature in the cascade system was much larger than that in the combined system as the hot water supply temperature increased from 55 to 75 °C. The CO2 discharge pressures in the cascade system were much lower than those in the combined system under all working conditions. The heating capacity in the two cycles was then examined in the two systems. The results showed that the CO2 cycle played the major role in the combined system while the R134a cycle played the major role in the cascade system. The system COP comparison showed that the cascade system performed better under relatively low ambient and hot water supply temperatures whilst the combined system performed better under high hot water supply temperatures. The compressor displacement ratio comparison results showed that the combined system would be much more environmentally friendly in comparison to the cascade system.

Air source heat pump systems have been widely used for domestic hot water and residential heating in southern China because they are much more efficient than traditional heating technologies such as electric heating and coal-fired boiler heating. Experimental investigations about an air source heat pump water heater (ASHPWH) operational performance were conducted in an environmental chamber with the variation of dry bulb temperature and wet bulb temperature, in order to accurately reflect and evaluate the actual operational performance of air source heat pump system for hot water supply. The results show that with the increase of water temperature from 30℃ to 54.2℃ the COP decreased, it respectively decreased 43%,48%,51%,64%,48% in the environment with ambient temperature at -7℃, 2℃, 7℃, 20℃, 30℃, and the average COP decreases from 4.0 to 1.96 while the elapsed time increases from 85 minutes to 295 minutes as the ambient air temperature drops. Annual operational performance was analysed in three typical city in south China. The findings indicate that annual performance factor (APF) of the ASHPWH in typical meteorological conditions of Guangzhou reached 3.35, while APF in Kumming and Nanjing decreases of 11.3% and 12.2% respectively.

A model predictive control (MPC) has been implemented in a medium-sized office building in Brussels, Belgium. This paper presents the implementation of the controller and the measured performance in comparison with the default, rule-based control (RBC). The building has two floors and a total size of 960 m 2 . The controllable system is the hybrid heat production consisting of two air/water heat pumps and a condensing gas boiler. The practical situation does not allow controlling end-units in the different zones of the building. The MPC makes use of a Modelica grey-box control model resulting from a system identification with monitoring data. The paper covers the monitoring, model identification, forecasting of disturbances, state estimation, formulation and solving of the optimal control problem (OCP) and transmission of the control signals. The performance is evaluated on a daily basis based on analysis of heating degree days, thermal comfort, energy costs and primary energy consumption. The results show that the model predictive controller is able to provide a similar or better thermal comfort than the reference control while reducing the energy costs by more than 30%. This is due among others, to a better use of the heat pumps and an adapted hot water supply temperature.

In this study, a wall mounted solar concentrating collector with parabolic and involute mirrors combined with an evacuated glass tube is designed to boost the solar energy collection for domestic hot water supply during winter. To optimize the device, the mirrors' parameters are varied, and the amount of collected energy in each case compared through ray tracing simulation. The results show that with the optimal mirror shape, the amount of collected energy is 5.5 times bigger than when the evacuated glass tube is set alone. This system will be considered sufficiently useful as it can reduce the high cost component of the evacuated glass tubes by replacing them with inexpensive mirrors.

The public bath is the emphasis target of energy-saving renovation of existing public buildings in China. In that case, the integration of the hot water supply system according to the characteristics of heat sources should be studied and optimized to improve the comprehensive energy efficiency and the hot water production of the system. This paper analyzed and remedied the deficiencies of several common hot water supply systems with multi-heat-source, introduced a novel hot water supply system with multi-heat-source based on PVT (photovoltaic and thermal) heat pump and water source heat pump, and then carried out the integrated optimization research of this new system. The main studies include: (1) Established the novel hot water supply system with multi-heat-source and the calculation model of system heating characteristic. (2) Introduced the evaluation method of the comprehensive energy efficiency and economic performance for the hot water supply system with multi-heat-source. (3) Aiming at reducing the total cost of hot water supplying, the integration optimization ideas of system were proposed. By above methods, the integrated optimization of the existing North Mountain Public Bath in Dalian University of Technology was conducted. On one hand the daily production of the existing hot water supply system in the public bath is increased from 80 t to 146 t, the supply capacity of hot water is significantly promoted. On the other the total cost of hot water supplying decreases from 9.6 RMB/(t year) to 4.9 RMB/(t year), the comprehensive energy efficiency and the economic performance of system is improved.

This investigation deals with the issues of resource-saving in buildings, to wit, power saving in heat supply systems. The IAHSU was considered as one of the solutions. The article gives an example of selecting an IAHSU for a 16-storey residential building and calculates the parameters required for making a HSU.

We report the epidemiological investigation of a nosocomial pneumonia case due to Legionella pneumophila linked to a contaminated hospital cooling tower in an immune-compromised patient. A 73-year-old female patient was diagnosed with nosocomial Legionella pneumonia proven by a culture of L. pneumophila serogroup 1 from bronchoalveolar lavage fluid. Two strains isolated from the patient and two strains isolated from two cooling towers were found to be identical using repetitive-sequence-based-PCR with a 95% probability. This Legionella pneumonia case might be caused by aerosol from cooling towers on the roof of the hospital building which was contaminated by L. pneumophila. We increased up the temperature of hot water supply appropriately for prevention of Legionella breeding in an environment of patients' living. On the other hand, as the maintenance of cooling tower, we increased the frequency of Legionella culture tests from twice a year to three times a year. In addition, we introduced an automated disinfectants insertion machine and added one antiseptic reagent (BALSTER ST-40 N, Tohzai Chemical Industry Co., Ltd., Kawasaki, Japan) after this Legionella disease, and thereafter, we have no additional cases of Legionella disease or detection of Legionella spp. from the cooling tower or hot water supply. This case demonstrates the importance of detecting the infection source and carrying out environmental maintenance in cooperation with the infection control team.

Most buildings in Hong Kong are served with electric/gas water heaters for hot water supply. With the elevated aspiration on the quality of life, an increase in hot water demand partly contributes to the escalating energy use of the city in the past decades. A photovoltaic-integrated solar heat pump (PV-SAHP) system, which can be seen as a scientific merge of the photovoltaic/thermal and solar assistant heat pump technology, is here proposed as a sustainable alternative. Numerical analysis has been carried out making use of a dynamic simulation model and the TMY weather data of Hong Kong. It was found that the proposed system with R-134a is able to achieve a yearly-average COP of 5.93 and PV output efficiency of 12.1%; the energy output is therefore considerably higher than the conventional heat pump plus PV “side-by-side” system. Within a year, the PV-SAHP system has better performance in summer time, when the monthly average COP could reach six or higher. Hence its application potential in Hong Kong is good.

To reduce the Legionella-linked risk in the several sites of Sud-Francilien Hospital, following a hospital-acquired legionellosis case, a multidisciplinary working group performed an action plan monitored through Legionella pneumophila counts in hot water supply. From 2003 to the first half year 2009, positive points for Legionella pneumophila in the main sites of the hospital decreased from 85.71 to 28.00%, representing a significant reduction of 67.33%. Similar results were observed for three of the four establishments, whereas the last did not describe a pronounced reduction of Legionella pneumophila counts and showed constantly serogroup 1 strains. During this period, investigations of additional cases of legionellosis demonstrated a nosocomial transmission in one case in this last site. Multidisciplinary mobilization in management of Legionella-linked risk contributed to these results.

To cope with the sustainability and conservation needs, window technology is currently under rapid evolution. A number of innovations in recent years have given window glazing a revised identity as well as a wide range of design options. This paper gives a brief overview of the developed as well as emerging advanced window technology for cooling-demand climates. The physical structure and energy performance are discussed and compared through numerical computation. Then the innovative concept of water-flow window is introduced and the potential areas of application are discussed. Our results indicate that this new design is able to support hot water supply system, reduce air-conditioning load and enhance thermal and visual comfort.

The green buildings of Shanghai Research Institute of Building Science include an office building for the demonstration of public building and two residential buildings, which are for the demonstration of flat and villa, respectively. Here, a solar-powered integrated energy system including heating, air-conditioning, natural ventilation and hot water supply was designed and constructed for the office building. However, only solar hot-water systems were installed for the flat and villa. All the three solar thermal systems have continuously run for 2 years. Two different integrated approaches have been put into practice in the two green residential buildings. It is shown that, for new buildings, solar collectors can be mounted on balconies and awnings besides roofs, on condition that solar systems become part of the general building design. The solar-powered integrated energy system has the advantage of high utilization ratio with different functions according to different seasons. It is testified to be capable of taking on about 70% of the yearly building load regarding the involved space under the weather condition of Shanghai.

Effect of using different obstacles on thermal stratification in a cylindrical hot water tank is analyzed numerically. The numerical method is validated using both experimental and numerical results. Temperature distributions within the tank for 12 different obstacles are obtained. The results indicate that placing obstacle in the tank provides better thermal stratification compared to the no obstacle case. The obstacle types having gap in the center appear to have better thermal stratification than those having gap near the tank wall. The obstacles numbered 7 and 11 represent better obstacle shapes and configurations for thermal stratification among the considered cases and consequently the tanks with these obstacles can supply hot water at higher temperatures. Other obstacle types have little effect on improving thermal stratification in the tank. Further comparisons of obstacles 7 and 11 in terms of the temperatures of hot water supply indicate that the obstacle 11 provides the best thermal stratification in the tank among all the considered cases. (c) 2005 Published by Elsevier Ltd.

Investigations elucidate how a glass cover with antireflection surfaces can improve the efficiency of a solar collector and the thermal performance of solar heating systems. The transmittances for two glass covers for a flat-plate solar collector were measured for different incidence angles. The two glasses are identical, except for the fact that one of them is equipped with antireflection surfaces by the company SunArc A/S. The transmittance was increased by 5–9%-points due to the antireflection surfaces. The increase depends on the incidence angle. The efficiency at incidence angles of 0° and the incidence angle modifier were measured for a flat-plate solar collector with the two cover plates. The collector efficiency was increased by 4–6%-points due to the antireflection surfaces, depending on the incidence angle. The thermal advantage with using a glass cover with antireflection surfaces was determined for different solar heating systems. Three systems were investigated: solar domestic hot water systems, solar heating systems for combined space heating demand and domestic hot water supply, and large solar heating plants. The yearly thermal performance of the systems was calculated by detailed simulation models with collectors with a normal glass cover and with a glass cover with antireflection surfaces. The calculations were carried out for different solar fractions and temperature levels of the solar heating systems. These parameters influence greatly the thermal performance associated with the antireflection surfaces.

A 6000 m 2 solar pond was constructed at Bhuj in India in the premises of a milk processing dairy plant to supply process heat and demonstrate the technical and economic viability of solar pond technology in the Indian context. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (low density polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of 99.8°C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried out subsequently indicated that the leakage was caused by the combination of high stagnation temperature and large air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993. Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruption of nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj Solar Pond was US$90 000 (1997 prices), including heat exchanger and piping etc., corresponding to a unit cost of US$15 m −2 .

To prevent fatal outbreaks of Legionnaires' disease, particularly in hospitals and other health-care premises, building services engineers are recommended to store and operate hot water systems at a temperature of 60°C. However, water at this temperature can cause serious scalding. It is therefore advised that mixing valves be installed in the hot water supply pipework to provide hot water at safe temperatures for washing and bathing. Electricity Association Technology Ltd (EATL) investigated the performance of three makes of automatic mixing valve. Tests showed that with constant supply conditions there was little difference in performance between the three valves when blending hot and cold water. However, the ability of the valves to respond to the loss of the cold water supply was quite different. Of the three mixer valves tested only the Horne 15 thermostatic valve was able, consistently, to shut the hot water off in the event of cold water failure. These results suggest that where it is necessary to safeguard people or patients against any risk of scalding, e.g. young children and handicapped patients, a quality thermostatic valve should be installed rather than a cheaper tempering valve.

To estimate future energy consumption for the Soviet residential and commercial sector, a simulation model has been developed allowing various scenarios of economic development to be calculated. The impact of social, economic and technical factors on the levels and structure of energy consumption has been taken into account. The forecast of energy consumption has been made for the following main energy uses: space heating and airconditioning; hot water supply; cooking; lighting; household appliances; and services.

The humidification trays of five of seven incubators in a neonatology unit of a hospital were found to be colonized with Legionella pneumophila , serogroup 1. Bacteriological analysis of the water in the humidification trays showed very large numbers of heterotrophic bacteria, one of which also contained Pseudomonas aeruginosa . Two hot water systems supply the neonatology unit, either of which is used to add water to the humidification trays; one system (A) is maintained at about 60 °C, while the other system (B) is maintained at 45 °C. The latter was also found to be colonized with L. pneumophila , Sg1. Monoclonal antibody (Mab) subgrouping of the isolates, indicated that system B was the source of colonization of the humidification trays of the incubators.

An experimental investigation has been carried out on a thermosyphon solar water heater. The system consisted of a flat-plate collector of 1.5 m2 absorber area with 21 tubes/m width and storage tank of 125 litre capacity. Experiments were carried out for both cloudy and clear weather conditions in winter and summer. The hourly system performance was evaluated for all test conditions. The final mean tank temperature was measured daily which enabled the calculation of the possible contribution of solar energy for domestic hot water supply in Basrah, Iraq (latitude 30.76°N). The system was tested at both no-load and loading conditions. Intermittent and continuous load was imposed, and system performance was evaluated for each condition.

An extensive analysis of solar heating and dwellings in eight cities in the U.S.A. has been completed by the authors and recently published. The design of the solar heating system was optimized in each location, and the cost of solar heat was determined. The mathematical model of these systems has now been modified to include heat-operated absorption cooling units of the aqueous lithium bromide type. Approximately one hundred analyses of hourly cooling (and heating) performance for a full year in these locations have been made. Designs have been reoptimized to minimize total annual energy costs for house cooling and heating and for hot water supply. The combined system has been found more economical than heating alone in most locations, and some locations unattractive for solar heating have become candidates for the combination. The paper contains a description of the method of computation and the results of the design and cost analyses.