5.0 Discussion 5.0 and concluding 5.0 remarks Despite much lower capital cost, electric panels in Option 2a and 2b have led to high operational cost and hence higher NPV against baseline. In both cases of electric panel and heat pump space heating, Option 2b and 3b demonstrated improved NPV when using continuous ow water heaters instead of electric-based water heaters. In terms of energy performance and costs, separating the space heating and DHW allows each system to operate more efciently. In both the base case and Option 1, there are modulating condensing boilers with weather compensation, but whenever there is simultaneous requirement for space heating and DHW, the base case boilers will not operate as efciently because the DHW results in higher return water temperatures to the boilers. The seasonal efciency of the base case boilers doing both heating and DHW is around 89%, compared to the seasonal efciency of the space heating boilers in Option 1 at around 91%, while the continuous ow water heaters is around 95% as these are optimised for hot water generation. A similar effect is seen between the options with heat pumps, where Option 3a with heat pumps providing both space heating and DHW has a Seasonal Coefcient of Performance (SCoP) of around 2.4, compared with 3.1 in Option 3b where the heat pumps are only providing space heating. The costs of distribution pipework generally dominates the capital costs, which is why the options with electric panel point heating have the lowest capital costs (at the expense of very high energy costs and overall lifecycle costs). Between systems with hot water storage and those with continuous ow water heating, the capital cost is generally in favour of the continuous ow water heaters due mainly to the savings in the cost of the storage cylinders. The operational CO2 emissions over 20 years show dramatic differences between gas and electric based heat sources, with Option 3a generating around a third of the CO2 of the base case with electric-based heating shown to be lower carbon over the medium/long term than gas-based solutions. The projected changes in CO2 intensity seems fairly optimistic and would require continual investment and the uptake in renewable technologies over the longer term to deliver the projected grid decarbonisation, which is highly dependent on political and economic pressures. Furthermore, in practice, there is unlikely to be sufcient capacity for major shifts in heating fuel from gas to electric due to the limited capacity of the national grid, unless this is supported by urgent aggressive investment in the relevant infrastructure. The analysis of the annual heat losses in the distribution pipe work show that the heat loss through the space heating pipes is between 22% and 25%, while for DHW pipe work it varies from 35% to 39%. This indicated potential savings could be achieved through distributed instead of centralised generation, both in terms of energy and capital costs due to reduction of distribution pipework. The study has shown that the various parameters considered vary signicantly depending on system type and hence for a more informed view, a lifecycle approach is required. It is prudent to revisit and review the compatibility of current system solutions, accounting for lifecycle factors such as the projected shift in grid carbon content and energy costs, so to be able to make any noticeable improvement in the long term resource efciency of the built environment. Full report available on direct request email sales@rinnaiuk.com For more details on RINNAI products visit www.rinnaiuk.com 82 November 2019 www.cibsejournal.com Advertisement Feature p82.CIBSEMagNOV19.indd 82 22/10/2019 15:21