DESIGN : DEAR PLUMBERS 33
Off-peak water heating
By
D . S ( Vollie ) Brink Pr . Eng . MSAICE , MPMISA
I have reached a stage in my life where I have decided to drastically reduce the use of paper and save some trees .
I had a large library of box files ( more than 60 ) with selected engineering information which I have collected over many years , and which are very valuable for training and for the transfer of knowledge . The information collected was also the type of information which you won ’ t find in formal textbooks .
Many engineers over many years came to my office to borrow these files to study the contents and learn from it and this was a great pleasure for me .
These files were marked to make it easy to find information , but I also had some ‘ General information ’ files which I cleaned out , and I found some papers with interesting technical information as well as one on ‘ off-peak water heating ’ – something not many designers know about .
This took me back to when we designed the hot water generation plant for a very large high-rise building , we designed the system to use off-peak power . The building was a very large office building with a few thousand workers , with a gym and large kitchen facilities , and therefore a large demand for hot water . The building also had a large demand for electricity during the day and very little demand for electricity at night .
We then investigated the possibility of using off-peak electricity to generate the hot water required to save on operational cost . We found that there was enough off-peak electrical power available during the night to generate all the hot water required for all the hot water needs in the building .
We designed a system with large enough storage vessels and very good insulation which generated enough hot water for the building during the off-peak hours . The outcome was that the capital cost , with interest , was paid back in 1.5 years .
On large buildings with off-peak electricity , it is important to consider the possibility to use it for hot water generation . The use of waste heat from the air conditioning should also be considered for use for hot water generation as it can also render cost savings .
It is also important to investigate the possibility of making it a requirement to upgrade the existing hot water system of a house when the existing geyser needs to be replaced – perhaps a subsidy ?
Carry-on plumbing ! Kind regards , PA
Vollie
Vollie Brink is one of the industry ’ s longest-serving wet services engineers . He continues to serve on SABS committees and has been involved in the Green Building Council ’ s Green Star rating system . Brink continues to consult for various organisations while enjoying a wellearned retirement .
“ On large buildings with offpeak electricity , it is important to consider the possibility to use it for hot water generation .”
February 2022 Volume 27 I Number 12 www . plumbingafrica . co . za