Energy Efficient Stationary Engine Block Heater
Block Heaters: With Circulating Pumps vs. No Pump
Block heater with circulating pump to reduce energy use.
Item ID: 381
Commercial, Industrial, Agricultural, Utility
Process Loads & Appliances--Commercial and Residential Appliances
Emergency backup generators must be ready to start at a moment's notice in order to provide continuous support to critical loads and safety equipment. To ensure that generators start quickly and reliably, they are required to keep the generator block warm with a water-jacket temperature of100 to 120 degrees F.
Block heaters typically consist of a simple resistance heater affixed at one of several locations to the engine. Convection circulates heated fluids in a process known as thermosiphon. These systems heat the engine block unevenly and inefficiently and may deteriorate piping materials.
Replacing thermosiphon heaters with electrical pump heaters can provide up to 55% in energy savings. Actual savings vary considerably, most dramatically with piping configuration. When the heated fluid enters the generators adjacent to the generator thermostat, it may be automatically directed to the radiator and lost. This measure has already been incentivized by several utilities including Avista and the Bonneville Power Administration.
Replacing the resistance electric heater with a heat-pump water heater can provide additional savings – up to 80% savings compared to a standard convection-resistance block heater. These systems utilize the resistance thermosiphon system as a second stage and backup heater during cold weather.
Baseline Description: Convection Block Heaters
Baseline Energy Use: 8560 kWh per year per unit
The baseline is an 1800W resistance block heater operating 4,755 hours per year. Total energy use is 8,560 kWh/year per block heater. 1800W is considered appropriate for a 60 kW- diesel generator (Grenoble, 2015).
Cooler climates equals a larger energy use, while a more temperate climate equals less energy use.
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 36%
Energy Savings Reliability: 6 - Approved Measure
The Bonneville Power Administration did a pilot study in 2012-2013. They partnered with five regional utilities that retrofitted a total of about 58 generator block heaters. Study results include:
- The energy savings reported varied considerably without a clear understanding of why in some cases, the savings were actually negative.
- Overall, energy savings increased with generator size, both in percentage and absolute value.
- A 1 MW generator with a block heater that ran all the time yielded 55% energy savings.
- A slightly smaller (900 kW) generator serving a data center yielded only 29% savings.
- A 15 kW wastewater plant generator block heater yielded 36% savings.
- Most case studies demonstrated a 30% savings.
- For systems where the heated fluid enters the generators adjacent to the generator thermostat, improving pipe configuration can result in similar savings as installing a forced-circulation block heater. Improving the piping and installing a forced-circulation block heater yields substantially higher savings than either retrofit alone.
As indicated above, one factor that significantly affected savings was piping configuration. When the heater fluid enters the generator too close to the generator's thermostat, the thermostat will open and send the heated fluid to the radiator where heat is lost to the area surrounding the generator more readily. For small generators (1 to 3 kW), heaters with a poor piping configuration had energy savings of 22-50%, while those with a good piping configuration actually delivered negative savings.
A 20 kW water plant generator heater yielded 27% savings after the block heater replacement, additionally savings roughly doubled up to 50% after the piping configuration was corrected to enter the generator far from the thermostat.
Another factor suspected to influence savings was location and climate; generators located outside in colder climates delivered greater savings in both indoor and outdoor installations.
Southern California Edison (SCE) found that when resistance, convective block heaters were replaced by heat pump block heaters with circulating pumps, energy consumption was reduced by about 75%. This was achieved despite the fact that backup resistance heaters needed to be operated when the ambient temperature dropped to about 50 degrees F to augment the heat pump, and to replace heat pump block heater when the temperature dropped to 40 degrees F. (Southern California Edison, 2009 Pg 1). Keep in mind that this study was performed in southern California, where temperatures fall below 50 degrees F far less frequently than the Pacific Northwest and other northern climates, and therefore the energy savings documented by SCE are likely higher than what would be experienced in the Northwest.
In a study by the Pacific Gas and Electric Company (PG&E), forced-circulation block heaters were found to offer energy savings benefits at ambient temperatures below 68 degrees F but not above that temperature (Edwin, 2014 Pg 15).
Note: This is a deemed measure under the October 1, 2014 BPA "Energy Efficiency Implementation Manual." The deemed amount varies by size and ranges from $200 to $1500 per unit.
Energy Use of Emerging Technology:
5,478.4 kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
Nationwide, 2,333,005 generators in the 3 kW to 4000 kW size range were shipped between 1991 and 2011. Given the typical life of a generator, this is reasonable proxy for the number of in-service generators. Generators between 3 and 4,000 kW have heating requirements from .5 kW to 12 kW, with the average aggregate savings potential equal to 470 aMW (average megawatts). The Pacific Northwest potential savings is roughly 4.3% of the national potential of 20 aMW. The BPA block heater savings potential is estimated at 8.48 aMW with the technical potential equal to 6.79 aMW.
This block heater technology is likely to be most cost-effective with generators that require heaters of at least 1.5 kW, which results in a reduced population of 571,843 generators nationwide or 4% of 571,843 = 22,874 standby generators in the Northwest. Note that some small portion of the shipped generators may be used for combined heat and power rather than as standby emergency power generation, and therefore would not require block heaters. However, that portion is assumed to be currently quite small so the population of generators wasn't derated. The national savings potential is reduced to about 1,762,379,348 kWh/year with the Northwest share being reduced to 4% of that total or 70,495,174 kWh/year when only heaters rated 1.5 kW and above are considered (this corresponds to those generators rated 30 kW and above).
With a regional savings potential of about 70,495,174 kWh/year, the average savings per generator is about 3,082 kWh/year.
Regional Technical Potential:
0.07 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $595.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $805.00
Baseline Technology Unit Cost (Equipment Only): $0.00
The typical installed cost of energy-efficient block heaters is as follows for various heater sizes:
(Boyer, 2014 Pg 46)
- 1 kW $1,200
- 1.5 kW $1,350
- 2.5 kW $1,500
- 3 kW $2,660
- 6 kW $2,770
- 9 kW $3,300
- 12 kW $3,950
Three-quarters of the generators in the BPA study had heaters between 1.5 kW and 2.3 kW. Assuming that this is somewhat representative of the region, an average cost for the retrofit is about $1,400. Note that where this is inserted in the field above, the entire cost is input as equipment cost, even though it actually includes labor. This is because this measure is all about retrofit, so the alternative is to take no action, and if there's a labor cost the cost-effectiveness calculation below will consider new construction.
The Bonneville Power Administration now offers incentives for implementation of forced circulation block heaters. For those below 3 kW, the incentive is $200. For those equal to or above 3 kW, it's $1,500. The retrofit project must replace a thermosiphon, electric resistance block heater on a stationary generator. The installer must be manufacturer-certified (BPA, 2014 Pg 112). Avista provides an incentive of $400 per forced circulation block heater (Avista, 2014). At this time, Tacoma Power also provides a rebate for block heaters.
Simple payback, new construction (years): 2.1
Simple payback, retrofit (years): 5.0
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.