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Lp Gas/Solar Water Heating Through the Seasons

Stokvis Energy Systems managing director Ivan Thompson reports a high level of interest from consultants, contractors and end users in the company’s solar thermal system for commercial applications.

Since the launch last year of Stokvis’ solar thermal system for commercial applications, we have had hundreds of enquiries and we have orders for new installations in both the commercial and public sectors. The fact is that, even in our northern climate, solar power is a viable option, because on a sunny day much of the UK experiences levels of solar energy that are equal to 60 per cent of those at the equator.

An evacuated tube solar collector linked to Stokvis’ lpg boilers and plate heat exchangers saves money by maximising the energy efficiency of heating systems, while also minimising heat loss through radiation. The ultra high efficiency Ecotube available from Stokvis Energy Systems radically reduces the amount of ‘parasitic’ energy (energy used up by the system itself when converting solar energy to heat) that is lost by most evacuated tube solar heating systems.

As a result, the system requires smaller pumps to circulate the fluid in the evacuated tube collector. This means that there are fewer drops in pressure through the system, giving a more sustained level of heat than most other systems.

Independent laboratory tests prove that the Ecotube produces more than 750kWh/m2 per year in direct heating mode and a staggering 850kWh/m2 per year in preheat mode. The system is an advanced form of evacuated tube collector that absorbs solar radiation and uses that energy to raise the initial temperature of a hot water system.

The energy absorber is simply a strip of aluminium treated with an advanced selective Tinox coating and bonded to a concentric copper pipe through which fluid is passed to collect the heat. The whole assembly is sealed within an evacuated glass tube and the vacuum that is produced virtually eliminates heat losses by convection or conduction.

Ecotube has a higher performance than flat plate systems and other evacuated tube systems because it benefits from the use of high transmittance glass that is virtually transparent to solar energy. A coating on the absorber plate maximises the solar energy absorbed and minimises the heat energy lost by radiation.

A durable glass-to-metal seal at the end of each tube maintains the high vacuum that prevents energy losses by convection and conduction and glass and metal components expand and contract at the same rate in response to temperature changes, resulting in a reliable system, whatever the season.

The concentric pipe direct flow design increases site flexibility by allowing the panel to be placed in any orientation. The panels are air temperature independent, so they work extremely well on cold, clear, frosty days.

The indirect system eliminates problems caused by the build up of limescale and also ensures that the system cannot freeze in winter. Automatic sensors prevent energy losses at night and during the darkest days of winter, and the use of a special heat transfer fluid eliminates any risk of freezing. Site flexibility is assured, as the panels can be installed flat on a roof, at an angle or horizontally on flank walls.

The system can be used in a wide range of applications. Solar water heating is an attractive option for housing associations thanks partly to government grants that can cover half the investment cost. Solar thermal heating systems can heat school swimming pools and provide hot water for use throughout the school premises, summer and winter.

It is also the ideal way to help businesses achieve their green energy goals and to mark them out as environmentally enlightened companies. Investing in solar energy is also cost effective for businesses since financial help is provided by government grants or Enhanced Capital Allowance tax relief.

Solar thermal heating, linked to an lpg gas boiler or water heater, is ideal for seasonal businesses, such as hotels, bed and breakfast establishments and caravan parks, where the demand for constant hot water peaks in the summer. The cost of providing the hot water required by en suite bathrooms, shower blocks and laundries can be prohibitive, particularly for smaller businesses and those that operate for only a few months each year. Lpg/solar thermal heating solves this problem at a stroke.

Contact Stokvis Energy Systems on 08707 707747 www.stokvisboilers.com

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