Industrial Vortex Generator – Cooling Tower (IVG-CT)

The majority of all cooling towers in the US and California traditionally use chemical treatment that is the entrenched conventional approach that can also waste water 1 . Commercial buildings alone spent 13,124 GWh in cooling and 6,937 GWh in refrigeration in 2012 in the California IOU service territories. Though much of the smaller equipment is air cooled, the larger cooling equipment and refrigeration systems use water cooled systems for efficiency. EPRI estimates that 6,985 GWh or ~35% out of the total 20,061 GWh on cooling and refrigeration is used in water cooled equipment. It also estimates conservatively, that 3.9 billion gallons of potable water is used in California cooling towers excluding evaporation, for just commercial buildings alone. Given California’s current prevailing drought conditions, this is a prominent concern. In the US there are approximately 500,000 cooling towers in 2010 and the number is growing2 . These towers use over 5 trillion gallons of fresh water. The goal of this three-month field assessment was to determine the efficacy of a physical water treatment (PWT) technology for cooling towers to determine energy, water, and chemical savings potential at a Southern California Edison (SCE) customer site. Although the assessment does demonstrate clear benefits it is recommended that a longer term assessment of a year be considered. Cooling Towers (CT) are heat exchangers that use water and air to transfer heat from chiller systems to the outdoor environment. The better the heat is transferred, the more efficient the cooling system is able to remove heat and allow the chillers to operate at peak efficiency and reduced energy consumption. The amount of water being reused or recycled in a cooling tower is measured using a term called cycles of concentration (COC). Essentially, the ratio of the mineral concentrations of the condenser water in relation to the makeup water or how many times the water can be circulated before the concentration of minerals gets too high and affects cooling tower performance. Cooling towers represent a significant water use at commercial and industrial sites. Based on a review of the Commercial Electricity use in the California IOU service territories, we have estimated that there is over 350 million gallons of water used by commercial cooling towers that could be saved in just three years by raising the COC from 3.5 to 5 COC. This presents a significant water savings opportunity in California if the COC can be increased. Water in the cooling tower is consumed in two primary ways: 1) water is evaporated from the tower to atmosphere3 ; and 2) water is sent to drain when the concentration of minerals has reached a preset limit. The PWT system being evaluated does not affect evaporation rates but does affect the possible COC enabling reduced water usage. A key consideration in managing energy and water in cooling tower operations is to reduce, or if the water quality allows, significantly reduce mineral deposition4 , metal corrosion, and microbial fouling. This is typically accomplished by introducing anti-scale, anti-corrosion, and anti-microbial chemicals into the cooling water. The PWT system as evaluated is not intended to eliminate all chemical treatment of the water alone; each site has its own unique water quality, but it can significantly reduce the volume of chemicals used. The majority of all cooling towers traditionally use chemical treatment. This is the conventional approach that the tested technology is intended to supplement with a more environmentally sound, consistent and efficient approach. The use of physical water treatment technologies for water-cooled cooling towers is growing in the U.S. and has been more widely used primarily in the EU where restrictions on chemical discharge and environmental policies encouraging lower water, energy and chemical usage are wide-spread. The technology assessed in this effort was established and is being deployed by Watreco A.B., Sweden and H2oVortex, Luxembourg in the EU. PWT technologies can offer advantages in controlling the primary water metrics of scale, corrosion, fouling and bacteria when applied properly, while reducing site water and energy use. Ultimately, every water management solution has a limit on how much water can be re-used without deposition causing negative impacts on heat transfer efficiency and asset protection. The energy and water savings are achieved by utilizing a controlled vortex flow technology to mechanically treat the water by creating extreme pressure gradients that, as a result, can limit or exclude the buildup of lime within the cooling tower water supply. The treatment process also eliminates micro bubbles in the water due to sub-pressure (vacuum) in the center of the vortex, resulting in a lower viscosity and an improved heat transfer capability of about 3%, according to the manufacturer. The purpose of this assessment is to determine if the energy savings claims can be verified. One aspect of the treatment is to preferentially precipitate the calcium bicarbonate as a form of aragonite and calcite that does not form lime scale on the various warm surfaces of the cooling towers and chiller.