Sustainability As with any heating system, the best time to
consider CHP is at the initial design stage, where it can be more easily integrated with all the required technologies. Specifying a well-designed system is key to the success of CHP, particularly when it is married with condensing boilers. The first consideration for any CHP installation should be the choice between ‘power led’ or ‘thermally led’ systems. For most commercial applications, such as hotels, student accommodation and nursing homes, the premise for using CHP is to maximise efficiency when supplying heating and hot water – which is deemed a ‘thermally-led’ design. This requires the system to utilise 100% of the heat generated to avoid unnecessary wastage at all costs. Achieving such a setup requires the CHP unit to be
correctly sized. Oversizing can limit the achievable savings, as well as prevent the unit from running effectively during the summer months, when the design load can drop as low as 15-20% of the total design load. By contrast, an undersized CHP unit will surely underutilise the technology’s potential. Subsequently, the best approach to sizing a CHP module is to establish the daily load profile of the building first, developing a regular pattern on a half hourly, daily, weekly and monthly basis. The more accurate the data, the more accurate the CHP sizing. Once this is translated into the correct CHP size requirement, a running time of 14-17 hours per day should be targeted. Another critical aspect of a CHP system is the selection and sizing of buffer vessels and thermal
Elco Heating Solutions’ Varion C-Power CHP units
stores. At this stage, it might be useful to clarify these two products. Firstly, a buffer vessel provides some thermal storage but is principally designed to provide (as the name suggests) a buffer effect between the CHP and the heating system. This protects the CHP from switching off
prematurely from short-term increases in return temperature. Thermal stores, on the other hand, are designed to hold excess heat produced by the CHP when the building’s heat demand isn’t sufficient. Installed between the flow and return circuits, while remaining full of water at all times, this reservoir of heat can be called upon when the building’s heat demand increases. When it comes to sizing a thermal store, the annual usage of the building needs to be considered,
where an hour-by-hour operating model is constructed; this will ensure CO2 emissions savings are optimised. Whereas, if the store is required to meet demand at times when the CHP is not operating, the quantity of heat energy to be held for the time period needs to be calculated. It is clear the UK will need to adapt over the
coming decades to a carbon constrained environment and, as a result, our approach to commercial heating and hot water production will need to evolve. Well-designed heating systems that meet modern sustainability requirements can help improve energy efficiency and reduce costs. As a result, CHP alongside gas condensing boilers represent one of the best long-term and truly economical options.
THE COMPLETE SOLUTION
Econoplate H Series - Heat Interface Units
Solar thermal panels and vessels
Econoplate - comprehensive range of
R40 Evolution wall mounted, fully modulating, condensing boilers - 6 models range from 56 to 130KW
Stokvis R600 Evolution floor standing, fully modulating condensing boilers - 7 models range from 142 to 540 KW
Econopress - complete range of electronic pressurisation sets
packaged plate heat exchangers
Heatpak - totally packaged plantrooms
THE CONSULTANTS’ & CONTRACTORS’ CHOICE. For further information or to receive a technical guide tel: 0208 783 3050 or email:
info@stokvisboilers.com
www.heatingandventilating.net
www.stokvisboilers.com October 2017 31
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