Gas prices this summer have provided an all-too-painful reminder of what utility costs can do to our wallets. With that in mind, the City has been working to keep more cash in our pockets by taking steps to be more energy conscious in heating and cooling City buildings. The City doesn’t have an official “buildings supervisor” so Gene Roberts, Public Service Director, has taken it upon himself to fill that role and over the last couple of years has started to consolidate the utility bills so he can start to track costs and identify consumption by building location over time. As a result of that effort, and a few minor changes in heating and cooling temperature settings, Gene has started to save the City money in energy costs. Here’s his recent summary.
Date: September 12, 2007
To: Dave Ruller, City Manager
From: Gene Roberts, Service Director
RE: Kent City Energy Management Policy
Please accept this memo in response to Kent City Council’s requested update of the Kent City Energy Management Policy implementation. On October 19, 2006 at the direction of Kent City Council, the following Energy Management Policy was implemented:
City of Kent Energy Management Policy
To better manage its financial resources Kent City Council directs the following Energy Management Policy implementation to improve the City of Kent’s Energy Conservation.
Immediate initial steps:
1. Set limits on all building thermostats as follows
- Heating, building occupied 70 °
- Heating, building un-occupied 64°
- Cooling, building occupied 76 ° – 78 °
- Cooling, building un-occupied 85°
Note: Typically occupied City buildings (excluding Police and Fire) are defined as un-occupied during nights, weekends and holidays.
2. In facilities where large sections of the building are un-used or used on a limited or part time basis set limits based on un-occupied when area is not in use. Cool or heat limited use areas prior to use and return to un-occupied thermostat settings when use is complete.
3. Where possible and appropriate all City HVAC units shall have retrofitted a programmable thermostat where such thermostat does not exist. No new HVAC unit shall be installed without a programmable thermostat.
4. Where programmable thermostats are not installed, the City Manager or Department Director shall assign the duty of setting the HVAC thermostat to the temperature settings outlined above and said employee shall daily set the appropriate thermostat setting at the beginning and end if each work day.
5. In buildings where the HVAC systems include fresh air dampers or exhaust fans both will be closed or shut down when the building is un-occupied.
Long term effort:
- Every staff member shall monitor building heating, ventilating and air conditioning usage and operation and report all concerns which they feel are wasting energy.
- Staff responsible for the City’s HVAC and building envelope systems shall inspect, maintain, repair and upgrade with a primary goal of decreasing the City’s consumption of energy.
The following overview is presented regarding the cost savings experienced after the implementation of the Energy Management Policy:
|Location||Total Cost/ HDD 2005||Total Cost/ HDD 2006||Total Cost/ HDD 2007|
|930 Overholt, Office Serv. Adm.||$ 56.46||$ 45.97||$ 39.17|
|1490 Enterprise Way , Shop Serv. Adm.||$ 78.36||$ 83.42||$ 50.93|
|319 S. Water St. , Police Dept.||$ 108.48||$ 135.39||$ 80.09|
|320 S. Depeyster St. , Fire Dept. Sta. 1||$ 143.98||$ 176.20||$ 87.66|
|325 S. Depeyster St. , B&F, Health & KCC||$ 35.81||$ 42.03||$ 24.68|
As can be seen above there have been cost savings experienced post policy implementation. The review of literature suggest that the savings should be viewed cautiously as the data is for only three years as explained in greater detail later in this report.
It appears that the cost savings are equally based on staff becoming more familiar in the second year and the additional equipment improvements that were installed in the summer of 2006. In addition to the summary provided above a detail for each of the buildings listed is provided as an attachment to this document.
Prior to quantifying the savings from the implementation of the Energy Plan a general understanding of the method used for the cost analysis follows:
An accepted method to quantify energy consumption is the use of Degree Day (DD) which is a quantitative index reflecting the demand for energy to heat or cool structure. In the United States, it’s agreed that 65° Fahrenheit (65° F) is the critical outside temperature; below this temperature heating is needed and above it cooling is needed.
The DD system has several problems. Heat requirement is not linear with temperature and each building has its own unique “balance point” which may be higher or lower then 65° F. Additional consideration must be given to solar gain which reduces the need for heating on sunny days (but not cloudy days), and wind which increases energy requirements (by an amount that depends on how tightly the building is constructed). The building contents can play a factor both for heating and cooling a building depending on the amount of heat which is given off from the equipments operation. Each time a door opens and closes also has an energy component and finally people differ in their opinions about what constitutes a comfortable indoor temperature.
DDs are further divided into Heating Degree Day (HDD) and Cooling Degree Day (CDD). If the mean temperature is above 65° F, cooling degree days (CDD) are recorded; if it is below 65° F, heating degree days (HDD) are recorded. The “heating year” during which HDDs are accumulated extends from July 1st to June 30th and the “cooling year” during which CDDs are accumulated extends from January 1st to December 31st. The total number of HDDs or CDDs recorded in any period of time measures rather accurately the demand during that time for fuel used in heating and cooling buildings.
T max = maximum daily air temperature
T min = minimum daily air temperature
Tavg = average daily air temperature
Tbase = base temperature for the type of plant or insect 65° F
DD = degree-days accumulated over one day
Use the HDD equation if Tavg is less than 65° F, use the CDD equation if Tavg is greater than 65° F and use neither equation if Tavg is equals 65° F. The higher the HDD or CDD number, the more natural gas for heating or electricity for cooling will be required.
It is important to remember that HDD and CDD run for 12 months (although with different starting dates) and if either formula results in a zero or a negative number of degree-days then the amount of degree-days is simply set to zero, meaning that no degree-days are accumulated for that day.
- Example for any given day:
High Temp = 50° F Low Temp = 20° F Average Temperature = 50° + 20° F = 35° F
Degree Day = 65°F – 35° F = 30° F Therefore, the day was a 30° day.
Although the degree day reading is useful, keep in mind that other factors such as sun load or excessive infiltration due to high wind also affect the heating requirements of a building and are not taken into account by the degree day calculation.
By taking the total Heating Degree Day figures and dividing it by the Days of Service, you arrive at the temperature variance from 65° F.
- For example:
507 Heating Degree Days
33 Days of Service = Approx. 16
65° F – 16 = 49° Therefore, the average temperature for those days of service was 49° F.
Where did 507 come from?
That figure comes from adding the heating degree day for each of the 33 days of service.
Day 1: 20° day Day 2: 10° day Day 3: 8° day Day 4: 23° day Day 5: 4° day… Day 31: 14° day Day 32: 13° day Day 33: 12° day Total for all 33 days = 507 Heating Degree Days
Planned work for the fall of 2007 includes updating the automatic HVAC controls at 325 South Depeyster Street and zone thermostats at 930 Overholt. Staff views the Energy Policy as one that will be ongoing, always evaluating current processes and looking to implement changes that will decrease the City’s use of energy.