Tapping into energy-efficient hot water

Improved profitability, greater energy efficiency, reduced carbon emissions – is it really too much to ask? When it comes to businesses with a high demand for hot water, implementing more intelligently designed solutions can provide the answer to all three challenges, argues Mike Hefford, Head of Renewable Technologies at Remeha Commercial

How would you rate a hotel or gym? A review of the key objectives for the hotel and leisure industry would invariably place service and comfort at the top of the list. Yet whilst the efficiency of the building infrastructure might not be rated as a unique category on a survey, the effectiveness of the building services is critical to the comfort of its visitors and guests and the success of the business.

Hot water is a case in point: a lukewarm dribble from the shower is hardly likely to encourage repeat custom. As heating water uses a huge amount of energy, addressing the efficiency of this service will not only help achieve more reliable, effective hot water delivery, but cut bills and improve profitability. It’s a clear example of an efficiency measure that enhances the customer experience whilst benefitting the hotelier or leisure centre operator.

A high percentage of the UK’s building stock relies on gas for heating and hot water. Condensing boilers provide a particularly effective, affordable solution to energy-efficient hot water provision, capable of achieving efficiencies as high as 98% GCV. The ErP Directive for heating and hot water products, now in force across the European Union, effectively makes it mandatory to install high-efficiency condensing boilers below 400kW, even on existing heating and hot water systems using non-condensing boilers, underlining the proven high performance of condensing technology.

With their lighter, more compact design, condensing boilers are quick and easy to install, which means minimum disruption to guests. The relatively low initial costs and rapid return on investment offered by this tried and tested technology also ticks the right boxes in terms of profitability, with future energy and carbon savings adding to the appeal.

So how do they work? Condensing boilers can achieve between 10 to 12% higher efficiencies than non-condensing boilers due to their ability to recover both the sensible and latent heat from the flue gases which is otherwise wasted by conventional boilers.

However, here’s the caveat: even with condensing boilers, energy can be wasted. Condensing occurs when the flue gases are at or below their dew point, which occurs around 54°C. For continuous condensing to take place, the boiler return water must be at this temperature or lower otherwise the higher efficiencies will not be achieved. For this reason, older heating systems sized on higher flow and return temperatures, typically 82/71°C, which are still found in many of our existing buildings, will prevent condensing boilers from fully condensing and achieving the maximum energy savings. Unless the system is designed to help promote lower return temperatures, or appropriate weather compensated controls are used, the building will be unable to reap the potential energy and carbon savings. For hotels housed in historic buildings, this should provide food for thought.

An additional factor for consideration, again especially for the hotel industry, is the fluctuation in hot water requirement throughout the year. A hotel at full occupancy will have a high demand for constant hot water to serve the kitchen and shower facilities. But what happens when the number of guests drops during the low season? Rather than over- or under-size the equipment, the challenge for heating manufacturers is to design a system that effectively meets both the continuous and peak demand of the building whilst maintaining maximum efficiencies and reliability and massively reducing the possibility of legionella.

To my mind, the simplest, most effective means of ensuring effective high efficiency hot water generation in a flexible, versatile solution that can adapt to the changing needs of the building is to utilise passive flue gas heat recovery (PFGHR) technology.

PFGHR devices can be incorporated into condensing boilers to make full-time condensing boilers that are able to operate at 100% efficiency regardless of flow and return temperatures or boiler load. These boilers work by recovering any waste energy and transferring it back through a Plate Heat Exchanger (PHE) for cold water preheat.

Investing in affordable PFGHR technology will bring a number of benefits to building operators and owners. Firstly, the reduction in energy consumption means lower fuel bills for improved profitability. Secondly, it cuts carbon which helps businesses meet environmental commitments. A third benefit from full-time condensing boilers is the reduced pluming: by lowering the dew point of the boiler flue gases, PFGHR effectively reduces the nuisance of the white vapour plume produced from the flue, helping comply with the Clean Air Act.

If we consider the modern multi-component plant room as a series of compatible building blocks, full-time condensing boilers are the centre from which we can create bespoke solutions to meet the individual requirements of a building. Full-time condensing boilers are factory-made, pre-plumbed and pre-configured units in cascade configuration that are delivered in a frame for easy installation. The modular arrangement supports improved reliability and helps achieve the maximum efficiencies.

Let’s take the hotel with its requirement for continuous and peak hot water demand. The initial step would be to select the number of boilers required to meet the continuous hot water demand. The inclusion of PFGHR would ensure that the boilers operate at maximum efficiency at all times for ultra-effective, reliable hot water delivery. The next step is to select a buffer vessel to store primary hot water for the periods of peak heat demand. If there is an allocation in the budget, there is also the option to extend this bespoke solution into a hybrid system by adding a gas absorption heat pump or combined heat and power unit and a control to further maximise energy and carbon savings.

For businesses with a constant high demand for hot water, keen to reduce their impact on the environment, make efficiency savings and increase their profitability, the good news is that the technology already exists to transform the performance of their buildings and boost their bottom line. Why waste when you can save? Where water heating is concerned, flexible, cost-effective PFGHR makes perfect financial and environmental sense.

This article originally appeared in BSEE magazine.



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