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.

"Typical" Savings: 36%
Energy Savings Reliability: 6 - Approved Measure

Comments:

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. 

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. 

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

Comments:

The typical installed cost of energy-efficient block heaters is as follows for various heater sizes:

• 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. 

Cost Effectiveness:

Simple payback, new construction (years): 2.1

Simple payback, retrofit (years): 5.0