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In many operations, within the industrial, construction and commercial sectors, the use of water is often an accepted process cost. There is scant attention paid to reducing such a significant service cost with fixing leaking taps often being the extent of energy saving in this area.
Industry uses water in many different ways and in different amounts, therefore water saving technology, in many cases, is used in multiple applications. The commonalities however are that highly efficient water saving techniques are proven to not only reduce an organisations carbon footprint but to also make huge savings on energy bills.
The simple fact is if an organisation can clean up this process water and re-use it just one more time it will effectively reduce its process water costs by a staggering 50%.
Yet, interest in this area of ‘process' is given little attention.
True, the re-use of process water involves the installation of additional filter technology to provide the necessary clean water. However, modern technologies and techniques can provide a significant return on investment.
If a process only uses 10 m³/hr (10,000 litres) and is a 24 hour operation, the water bill for this modest operation could well be in the region of six figures. Yet having the ability to remove solids of 1.0 micron and less, plus any additional treatments, to enable process water re-use would cost just £30,000 to £40,000 giving a payback within six months. Even with today's interest rates this is a fantastic return on investment.
Case Study 1
A plant manufacturing UPVC window sections typically uses 200,000 litres of water for the manufacturing process every hour which is traditionally treated with chemicals and chilled to 12-14ºC. With such a volume of water being used, a large recirculation tank and larger water chiller (2000 kW is not uncommon) is normally employed.
However, this process generates water contamination. In order to try and control this contamination many plants undertake an overflow of 20% of the volume every hour. This means paying for new fresh water at a rate of 40,000 litres every hour and at the same time paying for disposal of the same.
This approach however still didn't solve the process problems, as the remaining contamination still gave quality and process issues. However, by installing the correct technology over 90% of the UPVC industry now has better quality products with a near zero loss water system. Taking the following into account, a return on investment was achieved in less than six months:
- Reduced use of potable water (evaporation and spillage only)
- Reduced effluent charges
- Reduced product scrap due to better product finish
- Less energy expended on reworking scrap
- Reduced chemical use
- Reduced electrical energy (chilling water)
Case Study 2
In the commercial sector, for businesses that have large space cooling or heating systems the cost reductions are not based on the cost of the water, so much as the cost of electricity. These systems are often closed loop water heating or cooling systems. Typically, a chiller for a medium sized building with computers may well have installed refrigeration chillers which have 200-300kw of electrical energy. Larger buildings with high populations of personnel and computers can be much bigger.
Many public buildings require heating in winter and so use a combined system of chilled water and hot water. On the hot water systems this would be connected to the hot water boiler, very often driven by oil or gas. On the cooling side there is a cool water circuit, connected to refrigeration chillers to enable cooling to occur.
The energy input by the boiler or the chiller is significant whether using gas, oil or electricity to achieve the heating/cooling.
Ask any maintenance engineer what colour the water is in this system and this will range from pale straw (usually found in a new system) to black (found in a typical system). This discoloration is not just ‘yucky' it is actually having a major negative effect on the system.
From our experience, it is not uncommon to see large commercial buildings lose between 15-20% of its total heating energy input just because the water is dirty.
The discoloration is a product of the corrosion which is taking place naturally within the system, and this corrosion reduces the heat transfer from the heat source to the water, and then from the water to the heating/cooling outlet. A double energy whammy.
In addition, if chemicals are used to treat this dirty water, then the effectiveness of the chemical treatment will be reduced because of the high solid load within the water. Past examinations of this process have shown filtration to remove particulates down to 10 micron can improve heat transfer significantly, but our tests on many systems also shows that the majority of this contamination is between 1.0 micron and 10 micron. We believe that a saving of 15-20% in total energy costs in this process can be readily achieved
The solution is to clean up the heating/cooling water using reliable filtration to less than 1.0 micron connected to both the hot and cold water system. If the water in the system is anything but clear then energy is being wasted. The darker the water the more it is costing a business.
Making savings
So what are the savings against the cost of the technology?
A typical system using a 100kW chiller and equivalent heater can use 250,000kW per annum for a nine hour operation, five days a week. Many systems are running continuously to minimise energy losses so this figure could be as high as 870,000kW hrs per annum.
Assuming the losses are only 15%, this means a loss of 35,000kW per hour per annum. If the system is on 24 hours a day this cost increases to over 130,000kW per hour per annum, all of which could be recovered through investing in proper filtration which could give a return on investment in less than 10 months.
The Government has a big part to play if it is serious about reducing energy use and minimising the impact on the environment. But many potential ‘energy savers' are being put off investing in these technologies through lack of support funding and awareness of the true situation as illustrated in this article.
Yet the consequences of taking positive action by the Government, for what can only be described as responsible usage of water by industry, would not only reduce energy consumption significantly but also make huge cost reductions, and at the same time reduce the use of this valuable resource - drinking water.
The answer is in fact clear. The Government has to recognise water as a direct energy resource and bring the use of innovative water saving solutions into the funding stream. Everyone and the environment will benefit.
