Project Overview
Construction
Occupancy
Behavioural models
Demand
Renewable technologies
Conclusion
Team
Acknowledgements
Demand
Hot water
The half-hourly hot water heat demand can be determined from the half-hourly hot water flow rate according to the following equation:
where:
Mass flow rate results were taken from DHW-calc program (Jordan and Vagen, 2000). This program creates a list of flow rate values for each time step by distributing hot water draw-offs volume throughout the year with statistical means, according to a probability function set by user. Information needed to put in DHW-calc program are mean daily consumption of hot water, appliance hot water flow rates and probability of people using hot water at certain period of time during the day. It is therefore important to estimate all these parameters. All the input parameters for DHW-calc program are as follows:
Daily consumption of hot water per person
Source : Estimates of hot water consumption from the 1998 EFUS cited in BRE Housing Centre on behalf of DTI and DEFRA, 2005*
Appliances hot water flow rate
Source: Grant, 2002 cited in Magadley, 2009**
Probability of people using hot water
The probabilities of people using hot water follow the three occupant behavior models. The details of these probabilities, daily consumption of hot water and flow rate for three behavior models are attached here.
A specific heat capacity of 4.186 kJ/kg C was used in our calculations.
Approximation of inlet water temperature should be the ground temperature at site, however we assumed the ambient air temperature from Eskdalemuir climate data with limit of 10C minimum temperature as the ground temperature.
Hot water outlet temperatures were taken from the average from common household water temperature settings range from about 120 to 140F (approximately 55C) by NAHB Research Center (2002).
Results
The half-hourly hot water heat demand (q) can be determined from the half-hourly hot water flow rate according from the mentioned equation calculated by excel spreadsheet. Results of hot water demand load profile for three behaviour model can be downloaded from the link at the bottom of the page.
And the monthly hot water energy consumption for the previous the previously mentioned 3-2-1 combination would be the following:
The total monthly hot water energy consumption for the 6 houses would be 17380.56 kWh, and hence the average consumption per house would be 2896.76 kWh.
Hot water Demand Load Profile for Three Behaviour Models