HomeMy WebLinkAbout1979-08-07; City Council; 910-19; Municipal Swim Complex - Solar Heating*
CITY OF CARLSBAD
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Initial :
DeDt. Head AGENDA BILL NO. 911) - t #I9
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DATE : August 7, 1979 C. Atty
Pub I i c Works C. Mgr. DEPARTMENT:
S U 3 J E C 'T : MUNICIPAL SWIM COMPLEX - SOLAR HEATING
STATEMENT OF THE MATTER
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City Council instructed staff to investigate and prepare a report on the feasibility
ncluding solar heating in the Municipal Swim Complex project. Public Works staff
ted several solar installations, talked with designers and installers of solar
ems and, based on their findings, prepared the attached report.
Based on their studies, staff recommends the installation of a glazed solar panel system
with panel surface area equal to approximately 55% of the pool surface area. Location
of the panels should be on the roof of the main building and either on the roof of the
mechanical bui lding and on top of the west wal I (Area IfAf1) or in the northeast corner
of the pool deck area (Area "B"). While each location has its pros and cons, if it is
decided to install a solar system, selection of a final location should be the result
of consultation with the project architect.
The staff report con inues with an economic analysis of solar heating.
that the recommended solar system would result in an annual energy cost savings of
$17,000 to $18,000. If the amortized construction cost of the solar system were sub-
tracted from the energy cost savings we would still be saving almost $3,000 per year.
The findings are
The only unknown at this time is the architect's fee.
be in the range of $15,000.
It is estimated that it would
EXHIBIT
Staff report dated July 20, 1979.
RECOMMENDATION
That City Council authorize staff to negotiate a change in the design contract to include
the modification of plans and specifications to allow for the option of constructing a
solar heating system equal to approximately 55% of the pool surface area; and
That City Council authorize staff to approve the modifiation of the design contract pro-
viding the fee for the proposed work does not exceed $15,000.
AGENDA BILL NO. 910 - Supplement #19 Page 2
Counci 1 Action:
8-7-79 Council authorized staff to negotiate a change in the design contract to include the modification of plans and specifications to allow for the option of constructing a solar heating system equal to approximately 55% of the pool surface area; and
Council authorized staff to approve the modification of the design contract providing the fee for the proposed work does not exceed $15,000.
MEMORANDUM
TO: City Manager
FROM: Pub1 ic Works Administrator
DATE: July 20, 1979
SUBJECT: DISCUSSION AND STAFF REPORT ON SOLAR HEATING ALTERNATIVES FOR SWIMMING POOL
As the Council requested, staff has reviewed the proposals for solar heat- ing a1 ternatives. Basically, two a1 ternatives have been put forward:
1. The architect’s proposal of 28% solar heating.
2. A rather imprecise proposal by Great Western Solar (at the request of the value engineering team) to increase the percentage of solar heat- ing.
In response, staff reviewed the pertinent information, suggestions and recommendations and attempted to reduce the data to common parameters. Numerous solar consultants were contacted and the matter thoroughly dis- cussed.
A problem in analysis was comparing the so-called unglazed (plastic) solar panel versus glazed (glass) solar panel. systems have the single advantage of being cheaper per panel; however, this is offset by several disadvantages:
It appears that plastic
1.
2.
There is a lower heat gain per plastic panel.
Plastic panels require extra pump capacity to circulate the water at a higher rate in order to heat the same pool water.
More plastic panels are required (about 33% more).
The life expectancy of plastic panels is less than glass (about half).
3.
4.
The glazed systems and the plastic systems were quoted by several con- tractors at the same price (approximately $20/S.F. installed), which in- cludes pumping and fixtures. required will be 33% more, but not substantially different in capital cost.
If a plastic system is selected, the area
The plans were re-examined to find feasible locations for the solar col- lectors. dressing room roof:
Area A - The area over the mechanical room and westerly wall.
Area B - The northeast corner of the deck area. mounted on supports, providing a shady area on an otherwise sunny pool deck, or ground mounted (which would be less expensive).
The examination showed two possible areas in addition to the
Panels could either be
-2-
The dressing room roof could also be more fully utilized by providing tilt type panel mountings rather than flat.
A sketch of possible panel locations is attached.
Approximate cost data is provided on the attached graph. the graph note that there are two intersecting lines representing energy costs and solar installation costs. is based on a cost of $2.43 per square foot of pool area per year to heat a pool to 82" F. If there is zero solar panel area, the cost to heat the pool will be $31,259 per year ($2.43 x 12,864 S.F.). The amount of money needed now to generate $31,259 per year for 20 years at 6% interest is $358,540. This figure is the "present worth'' of future energy costs with no solar panels. At the other end of the scale, the "present worth" of future energy with all pool heating provided by solar panels is zero. The line representing solar system costs is based on $20 per square foot and at 25% coverage of the pool area is about $66,000; at 60% coverage is about $175,000. The intersection of the two lines on the graph represents the optimum point between solar panels and future energy costs.
Based on the graph, an expenditure of approximately $155,000 for solar panels could result in reducing energy costs from a "present worth" of $358,540 (or $31,259 annually) to about $155,000 (or $13,513 annually). Considering the $155,000 cost of solar panels amortized over 20 years, the annual net savings by using 50% solar panels would be about $2,700. The assumptions made in this argument ignore future increases in energy costs, inflation and other factors. the economy as they have in the recent past, the savings would be substan- tial ly greater.
The engineering staff would recomnend the installation of solar panels of the glazed (glass) type, providing about 55% coverage of the pool and mounted in til t-up fashion on proposed structures.
To understand
The line representing energy costs
If these factors continue to affect
T&L
Ronald A. Beckman, P.E. Pub1 ic Works Administrator
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