Table 1. Example Increases in Energy Consumption as a Function of Scale Thickness

Estimated Savings and Market Potential

As part of the NTDP (New Technology Demonstration Program) selection process, an initial technology screening activity was performed to estimate the potential market impact in the Federal sector. Two technologies were run through the assessment methodology. The first technology was assessed assuming the technology was applied to the treatment of boiler make-up water. The second technology was assessed assuming the technology was applied to both, the treatment of boiler make-up water and cooling tower water treatment. The technology screenings used the economic basis required by 10 CFR 436. The costs of the two technologies were different based on information provided by the manufacturers, thus leading to different results.

The technologies were ranked on a total of ten criteria. Three of these were financial, including net present value (NPV), installed cost, and present value of savings. One criterion was energy related: annual site energy savings. The remaining criteria were environmental and dealt with reductions in air emissions due to fuel or energy savings and included SO2, NOx, CO, CO2, particulate matter and hydrocarbon emissions.

The ranking results from the screening process for this technology are show in Table 2. These values represent the maximum benefits achieved by implementation of the technology in every Federal application where it is considered life-cycle cost effective. The actual benefit will be lower, because full market penetration is unlikely to ever be achieved.

Table 2. Screening Criteria Results

Energy Savings

Energy savings result from both, reductions in pumping energy input to the system and reduction in fuel consumption. The first aspect has not been well quantified by the users or in any of the case studies. It is thought of as a secondary benefit.

Fuel consumption has been lowered in every situation. The exact savings are a result of a number of factors:

• How effective the chemical scale control program may have been relative to the input water hardness.
• How often the heat exchange system was taken down for maintenance and cleaning.

On systems that were descaled frequently or had low scale formation, due to low hardness and/or an effective chemical scale control program, the savings in fuel consumption were lower, often from a few percent to as much as 15%. The lower savings were at an installation using ion exchange softening of moderately hard water (less that 150 mg/L as calcium carbonate hardness). On systems where descaling was infrequent or absent altogether, or where the chemical scale control program was not as effective in controlling scale formation, fuel consumption savings ranged up to 30%. This was found to be the case in a installation using very hard water (hardness in excess of 300 mg/L as calcium carbonate), and a chemical scale control problem, with heat exchanger tubes closing due to scale formation after less than one year. In each case the fuel consumption savings was proportional to the thickness of the scale layer removed.

One important note was that fuel consumption savings often trailed installation of the technology by a significant period due to the fact that the savings is driven by the amount of scale on the heat exchange surface. The accumulated scale will erode over time, resulting in fuel consumption reductions. For this reason, many of the manufacturers recommend installing the technology only after the system has been descaled, thus savings in fuel consumption should be immediate.