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Decarbonisation of the built environment

Decarbonisation of the built environment is a task that every architect and M&E Consultant is tackling on a daily basis. Strict goals set by the government to reduce carbon emissions within tight time frames means that all systems which consume electricity within a new commercial project are scrutinised with regard to their energy efficiency. In addition to this, other technologies are pursued with a view to assisting in reduction of energy consumption of a building.

One of the greatest energy consumers in commercial buildings is heating. Heating of the spaces and heating of the water for hand washing, showering etc.

It is a known fact that bacteria like warm environments, they attach to warm surfaces, multiply and lead to risk of legionnaires disease. What is not so widely known is that bacteria, in particular the biofilm that is created by widespread biological proliferation, is a fantastic heat insulator. Most buildings use either calorifiers or plate heat exchangers to transfer heat from the LTHW water circuit to the domestic hot water services. In a heat exchanger a 20 micron thick biofilm can cause up to 30% decrease in thermal transfer efficiency. Biofilm is significantly more insulating than limescale deposit.

Therefore, every effort is made in order to prevent biological activity in the water systems within a commercial building. The most common technologies implemented include chemical dosing, copper silver ionisation and Ultra Violet Sterilisation.

Chemical dosing requires manufacture of the chemical and transport to site on a regular basis to top up the day tanks which all add to the carbon footprint of the building. In addition, onsite H&S assessments and special storage areas are needed. The chemical works by either breaking chemical bonds within the molecules or reacts with the cell wall killing the pathogen

Copper Silver ionisation is very costly, not only from the capital outlay but also from an OPEX perspective. The positive ions released by the copper and silver billets bind to the negative cell walls of bacteria causing the protein cell to break down and eliminating the bacteria. Many countries have banned the use of this technology as it liberates ions into the water cycle which are not removed and have an environmental impact.

Ultra-Violet Sterilisation uses UV-C Photons generally in the range of 254nm to disrupt the DNA of pathogens preventing them from replicating, this effectively means they are dead. This technology is probably the most common out of all three of these solutions as it is clean and has a minimal onward OPEX. The UV system is mostly installed after the buildings CWST’s and booster sets.

The common issue with UV in a water circuit is that the UV lamp is always on, consuming 100% of its energy whether there is flow or not. These water systems, especially in commercial buildings which have a fluctuating occupancy with high demand during the day but very low demand in the evenings and weekends mean that water is called for intermittently. Standard mercury lamps don’t like being turned on and off as this degrades the lamp, and ‘warm up’ times of the lamps take minutes therefore they are always left on drawing power. The surface of mercury lamps also get hot, in normal flow conditions this heat is dissipated into the moving water however in stagnant flow conditions the lamps heat the surrounding water to temperatures in excess of 50°C. This high temperature is not only detrimental to the lamp, chamber and surrounding pipework (if uPVC or PE100 is used) but when water is drawn off again, warm slugs of water are dispensed from cold water taps. In order to manage this, modern UV systems use a temperature sensor linked to a solenoid valve post the UV install which flushes water to drain when a set temperature is reached allowing fresh water into the lamp chamber cooling the body and lamp down. The valve is shut off when the desired temperature is reached.

So, although Ultra-Violet Photons give us brilliant and clean pathogen control, the mercury-based systems do have draw backs which also add to the carbon footprint of the building, namely:

1. Energy use at 100% all the time, irrelevant of flow conditions

2. Water is wasted often to cool the lamp chamber in idle flow situations.

Enter LED derived UV-C photons.

LED’s have revolutionised the lighting sector offering low energy, high output lighting for years now, you hardly see old mercury fluorescent tubes installed anymore. In the same way that LEDs have surpassed old technology in the space lighting sector, they are now gaining momentum in the water sterilisation market. LED’s can be switched on and off in nano seconds, they can be switched an unlimited number of cycles and when turned on, they reach sterilisation intensity immediately. This means that in applications with intermittent water flow, the UV unit can switch off when water is not flowing and instantly switch on when water flows again, thus only using energy when required to kill bacteria, it also pulses the LED’s when water is idle for long periods. Additional power savings are achieved with our dynamic power modulation which manages the output power to the LED’s according to flow rate; further curbing the energy use. Modern medium and low pressure mercury-vapour amalgam lamps have a life of 8,000 to 12,000 hours which translates to replacement every 12 to 18 months, the LED modules have a similar life; however, the life only counts down when the lamps are in use therefore the LED modules last years before needing replacement.

LED UV technology does not implement mercury in its manufacture, mercury is a persistent, bio-accumulative, toxic pollutant. When released into the environment, it accumulates in water laid sediments where it converts into toxic methylmercury and enters the food chain. The Minamata Convention on Mercury was initiated by the United Nations Environmental Programme (UNEP) to protect human health and the environment from anthropogenic emissions and releases of mercury.

In 2013 the UNEP requested that organisations and governments discourage the use of mercury starting immediately unless there is a substantial benefit to the environment and human health. Although the Minamata Convention does not specifically prohibit the manufacture and sale of UV Mercury-vapour lamps, it does positively influence adoption of alternative technologies.

LED UV-C Systems Ltd are the UK distributor for the PearlAqua range of LED driven UV-C water disinfection systems. The PearlAqua range is the leading LED UV-C technology in the world boasting the highest number of system sales as well as the most certified LED UVC technology including NSF Regulation 4.

The PearlAqua line-up includes:

· The Micro, a small point of use device used in hospital critical water outlets, OEM applications and even in space!

· The Deca, a domestic point of entry system for borehole treatment and general whole house water sterilisation.

· The Tera, a high flow municipal water unit for treating flows up to 950m3/h.

Now to add to this already fantastic portfolio we introduce the PearlAqua Kilo, a mid-sized system suitable for flows of 20m3/h to 230m3/h and absolutely ideal for the large commercial building sector.

CO2 reduction is on everybody’s agender, however we still have to manage common risks associated with today’s built environment, pathogen mitigation being one of them. The PearlAqua Kilo UV system offers this balanced solution; clean water disinfection and intelligent energy use.

Contact us to find out more and specify the PearlAqua Ultra-Violet Water Sterilisation System in your next commercial, industrial, healthcare or domestic project.

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