Document Type

Restricted Campus Only

Publication Date

4-2012

Abstract

Consumers have numerous solar water heaters from which to choose. While these designs reduce the amount of money spent on power bills due to decreased energy use, there is a high initial cost associated with switching to a solar water heater, which could have payback period (the amount of time before cumulative energy savings equal initial cost) of 12 years or longer. As a result, a large population in San Antonio is reluctant to use a solar water heater continues to use conventional (gas or electric) water heaters. Switching the source of water heating energy from gas or electric to solar will reduce energy expenses. Introduction of low­initial-cost solar water heaters will encourage more of the population to switch to the more environmentally friendly solar water heating. San Antonio, which naturally has a reliable source of solar energy year round, is a favorable area to implement wide spread use of solar water heaters. The main objective for this project is to design a solar water heating system that is affordable to low-income families in San Antonio, Texas.

The solar water heater must meet design constraints in order to be considered successful. The most important constraint is that the water heater must have no greater than a two year payback period. This means that after two years all costs attributed to the switch from electric to solar will be offset by the savings on the power bill due to using less power from switching. In addition, the design of the solar water heater must meet all of the Solar Rating and Certification Corporation (SRCC) standards and regulations. This would ensure that the design is safe to the user, an acceptable product in the market, and qualified for the CPS Energy Rebate.

The design chosen to meet the project goals is a batch collector system. The collector was built and tested in order to measure the performance. Initial tests consisted of a prototype to test the effect of more or fewer layers of glass. Outdoor testing consisted of exposing the collector to the operating environment by placing it at the optimal angle to the sun on the roof of a four story building. By measuring the temperature of the water throughout testing, the performance could be quantified. The payback period was calculated to be 25 months by analyzing the system function and comparing it to conventional heater function.

The full system design will consist of two large tanks which can hold up to 40 gallons of water, in each tank, enclosed in a wooden frame with a glass cover. The design includes two tempering valves to control the temperature of the water delivered to the conventional backup water heater and the water delivered to the household. The final cost of this design is $3,000. A list of materials needed in order to create this design has been created as well as a list of vendors that can supply the material.

Since the expected cost of the design is greater than the budget ($1,200) a scaled down version of the actual design will be built, consisting of one collector and the attachments (thermostatic mixing valves and pipes) separately.

Comments

Project Advisor: Dr. Peter Kelly-Zion

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