Galati, Romania Case Study
Background
In the Apaterm Water Distribution System project at Galati, Romania, Cadmus discovered that a series of energy conservation measures could save roughly $250,000 per year in electricity costs. Low cost measures included trimming impellers to better match pumps and motors with required flows and pressures. Moderate cost measures included leak detection and reduction and limited pump replacement.
Galati's water system is supplied with raw water from a pump station operated by Sidex, a nearby steel plant, and a series of wells 30 km west of the city. Most of the system's water comes from Sidex. Apaterm, the city's municipal water utility, pays Sidex 3,000,000,000 lei, or roughly $125,000 per month for water.
Average daily water use of Galati is 210,000 m3 which translates to about 600 liters/person/day. Per capita U.S. consumption including leakage is roughly 378 liters/day. One would expect water consumption in Galati to be much lower than in the U.S. because, however this is not the case for the likely following reasons.
Leakage in the distribution system.
Leakage in water fixtures including showers and tubs, toilets, urinals, and sinks. The use of generic water bills (assumed use of 11m3/month/person), which do not encourage water conservation.
I. Savings from Leak Elimination
The city estimates that pumping 10,000 liters costs $0.13. Even a small leak can easily waste a large amount of electricity. A toilet constantly running can waste on the order of a liter/minute or 1,500 liters/day. Over a year this is roughly 500,000 liters or $7.00. If the leak can be fixed for $7.00 then the repair pays for itself in a year and generates an additional $35 in savings over the next 5 years. A comprehensive program that fixed 1,000 leaking fixtures could thus save $7,000 per year. Because labor in Galati is relatively inexpensive and the parts to fix leaks are also cheap (washers, seals, etc.) a leak detection and elimination program would rapidly pay for itself.
An initial goal for the city would be to reduce water use 1% or 2,640 m3/day through leak elimination and conservation measures. An ongoing program could achieve this level of reduction for 5 years resulting in a total reduction of 5 percent at the end of the program. This would save roughly $13,000 the first year. Savings for the first 5 years of the program are shown below.
Savings Available Through a Leak Detection Program
Year 1: $13,000
Year 2: $26,000
Year 3: $39,000
Year 4: $52,000
Year 5: $65,000
thereafter: $65,000
Based on the monthly fee reportedly paid to Sidex for water pumping, water conservation could yield double the savings above if that fee is included.
The cost of a leak detection program would depend greatly on the way it was organized and whether existing labor could be used or whether new labor would be needed. Because the water company's labor pool is relatively large, a leak detection and control program could potentially be run for the cost of parts and management, with labor pulled from the existing staff. The cost of the program could be phased and grown as the savings above grow, generating a positive cash flow. For example the pilot program could be designed to cost $5,000 the first year and grow by $5,000 per year thereafter. Based on the table above the program would generate $8,000 of net savings the first year, $16,000 the second year, etc.
Other Measures for Galati
Energy efficiency measure: Cadmus estimated that reducing the height of the discharge would decrease the static head between the wet well in a low voltage pump station and the actual discharge. If the height of the reservoir were an average of 1 meter below the discharge and the discharge were lowered, roughly 10 percent of the pumping costs could be eliminated. The cost of the measure would include labor and minimal parts (pipe extensions). This measure would save roughly 100,000 kWh/yr or $5,000/yr.
Replacing Pumps. For one pump's 5,854 hours of annual operation, it used roughly 2,500,000 kWh. A replacement pump and motor set could save roughly $55,000 per year. For another pump with 6,000 hours of annual operation and consuming 3,000,000 kWh per year a replacement pump and motor set could save roughly $42,000 per year.
Variable Speed Pumps
One pump in Galati's system runs roughly 5 hours per day. The throttling schedule has not been recorded, but the pump appears to be throttled during its nighttime operation. Cadmus observed periods when the header pressure was roughly 5.5 atm, but pump pressure was 7.4 atm. At the throttled condition, efficiency rises to 70 percent based on the pump test. This efficiency measure is based on replacing this pump with a high efficiency variable speed drive pump. Savings for this measure are calculated based on higher efficiency (75 percent), the elimination of throttling, and the assumption that the pump picked would achieve peak efficiency at the system operating point of 5.6 atm and roughly 2,000 m3/hr. The pump uses roughly 1,135,000 kWh per year at the measured flow and pressure during 1,825 hours of operation. A replacement pump and motor set could save roughly $19,000 per year.
Impeller Trimming
Another pump in the system is too large for its motor, although it can provide sufficient flow and pressure while heavily throttled. This was verified by reviewing the pump's power requirement curve and the nominal motor capacity. Additional verification came from the fact that, when we opened the valve to 40 percent, we were on the verge of tripping the motor circuit's breaker. We recommend that Apaterm trim the pump's impeller to better match it to system requirements and to its motor. In discussing this recommendation, Apaterm indicated that there are several short peak periods, roughly several hours per day for a day or two per year, when higher capacity is needed. Because of the limitations of the breaker and motor, we think that any additional flow needs are best met with a parallel pump assisting Pump 2. Assuming that the impeller can be trimmed to deliver 5,000 m3/hr at a system pressure of 6.46 atm without throttling, savings on the order of $100,000 could be achieved.
Contact: Angela Morin Allen at amorin@ase.org.