Feedback Readers discuss the proposed Swansea Bay lagoon, whether we are oversizing our domestic water systems, district heating costs and the timescale for smart offices An impression of the proposed Swansea Bay lagoon Lagoon fears Harnessing power by using lowcarbon means should be done in an economically, environmentally and ecologically acceptable manner. The proposed Swansea Bay lagoon (Budget backing for Swansea tidal lagoon, CIBSE Journal April 2015) involving a 9.5km-long, 26m high breakwater, enclosing 11.5km2 of mud flats and sea fails to satisfy these criteria because: It should be outside Swansea Bay potentially useful energy and exergy in the heat supply (for counterflow domestic water heating, for example) could result in a 15C return temperature. Such a system will give savings of more than 10% to producers and consumers because it will increase the efficiency of heat supply from CHP, electric heat pumps, biomass boilers and solar thermal. It will also minimise the volume of water that consumers take from the system, reducing distribution costs and losses, as well as ensuring that those remote from the source get heat at times of peak demand. William Orchard MCIBSE Note from editor The standfirst in last months opinion article by Paddy Conaghan (Time to change our BIM practices, CIBSE Journal April 2015) incorrectly stated that contractors and designers must work on the same model. Conaghan makes clear that while in an ideal world this would be true the current generation of Level 2 BIM platforms used by designers does not give contractors all the features they need. and enclose deeper seawater for example, at the upper reaches of the Bristol Channel coastline The proposed turbine design is inappropriate for Swansea Bay, because of rapid silt movements, and would lead to a deteriorating, power-harnessing electrical output The 16 turbines would function simultaneously for 16 hours per day, thereby not harnessing any power for one third of each day. The proposed lagoon would make the beautiful sweep of Swansea Bay less attractive and lead to increased sea pollution because of contaminated seabed disturbance and increased flooding of the seashore. For any UK government to agree to a strike price of 168/MWh as sought by the developer locked in for 35 years, would be financially profligate. To subsidise this 850m project would be a high-risk, ultraexpensive strategy, economically. Its failure would set back the technological cause of harnessing tidal energy in Britain for many years. Doug Probert, Emeritus professor of applied energy and the environment, Cranfield Postgraduate University Rewriting the standards The article on oversizing domestic water systems (CIBSE Journal April 2015) highlights a real problem with standard mechanical services design, and reflects the issue of diversity that I discussed in my article on lean design (CIBSE Journal June 2014). The findings on actual hot-water use in apartment blocks indicate that using BS6700 overestimates predicted use by a factor of 10. This month, CIBSE LinkedIn group considers the timescale for smart office buildings Ken Dooley How many years are we from having fully smart office buildings, with ventilation, lighting and equipment controlled by occupancy sensors? Michael Brankin Lots of buildings with good BMS control over the heating vent and cooling energy, and good lighting control, can be considered smart. However, the best ones were designed years ago, when the services consultant worked for the client. Nick Hudleston All the fancy front-end, internetenabled, mobile tech in the world is useless without robust scientific research into control algorithms, and maintaining that scientific approach postoccupancy. Tony Thurgood Until owners and their backers change their funding mindset, in this current dark-age, set-in-stone economic environment, it will n ever happen. Roy Gee Until clients, accountants and engineers remove the word payback from progressive solutions, take-up will be much slower than it should be. If it doesnt have a payback of three years or less, it will struggle to be implemented. Oversizing wastes clients money, leads to inefficient system operation and gets building services engineers a bad reputation. Time to rewrite the standards! Matthew Hill MCIBSE Consulting engineer and director at LEDA The cost of district heat The recent Which? update on district heating raises strong consumer concerns about the cost of heat supplied in district heating. To provide more appropriate charging and, importantly, to ensure end-users systems are designed to extract the maximum potential heat a simple solution is to pay for heat just as we do for gas, so that payment is based on its potential energy. Heat metering results in consumers paying only for the energy they extract. This potentially allows end-users to return water into the district heating distribution system at high temperatures; having feasted on the supplied high temperature, it can return the water just a few degrees cooler than when it was taken. A proper application of the David Cowlrick Until we have maintenance personnel with an understanding of the installed systems, smart buildings june not stay that way for long. Gersil Kay Net-zero energy, complete automation, and Internet of Things june never be achieved because people are so unpredictable. One careless user could sabotage the best plan. Full-time inspectors on every component still would not cure the problem. Smart buildings are sometimes dumb when one of the connected systems fails and brings the rest down with it. Simon Owen There is a lot to be said for passive solutions that have been properly thought out, and where occupants are familiar with how it works. CIBSE Journal welcomes readers letters, opinions, news stories, events listings, and proposals for articles. Please send all material for possible publication to: editor@cibsejournal.com, or write to Alex Smith, editor, CIBSE Journal, CPL, 275 Newmarket Road, Cambridge, CB5 8JE, UK. We reserve the right to edit all letters.