Wisconsin's "Orphan" Solar Program

by Jeff DeLaune, Chip Bircher, and Richard Lane

One utility found that rehabilitating old solar water heaters amounted to a cost-effective energy conservation program

In July 1993, Wisconsin Public Service (WPS) and Public Energy Systems (PES) began to evaluate the condition of existing Solar Domestic Hot Water (SDHW) systems as a precursor to a New Install Demand-Side Management (DSM) program. Wisconsin's Public Service Commission had ordered WPS to aggressively market a solar water heater program. WPS had always allowed SDHW rebates under its "Custom Rebate" program but the new program would require an inventive and active marketing approach.

WPS reviewed the history of solar installations as background to developing this new program. An unsettling number of stories described under-trained contractors installing systems whose components had not undergone sufficient testing. Most of these contractors went out of business when solar tax credits ended in 1986. The result was homeowners with systems that failed and no contractor to contact.

WPS decided it was necessary to analyze these system failures in order to design a new install program that would not repeat the same problems and conditions. Unfortunately there has been no coordinated national effort to collect and disseminate information and "lessons learned" from earlier programs. PES, formerly Packerland Solar Systems, of Green Bay, Wisconsin, was contracted to locate and inspect SDHW systems in and around Green Bay and to collect the necessary information. We named the program "Orphan Solar" because we expected that these systems were all but abandoned by original installers and possibly even by their owners.

In addition, we assumed the installer infrastructure was basically nonexistent. Customer and intervener groups had pressed WPS for a SDHW "rebate" program. However, when we first offered one in 1993, this interest was left unsupported by contractors.

The goals of the program were to

• Determine common causes of system failure and improve the program design of WPS's new install program to lower the failure rates.
• Determine the condition of system components after years of use under actual operating conditions in order to better estimate system life expectancy and energy production.
• Determine customer perceptions and satisfaction with solar heating equipment.
• Overcome lingering negative perceptions homeowners might have with the technology.
• Return systems to working condition in order to capture energy savings for WPS's DSM program.

The last goal was almost an afterthought, and was included as a way to compensate owners for the inconvenience of the inspection.

Finding the Orphans

Locating the systems was not as easy as we expected. WPS estimated there should be approximately 2,000 solar heating systems in its service territory. However, a survey conducted by WPS meter readers turned up only 178 systems of all types. A search of WPS's residential audit database located an additional 18 systems. WPS finally resorted to paying PES to manually search through a paper record of state tax credit recipients to locate installed systems. PES was able to find over 1,500 additional systems from this list.

Initially the procedure was for PES to mail a postcard explaining the program to customers before a telephone contact was made. During the phone call, PES was to determine if the solar system was still installed, if it was a SDHW system (as opposed to space heating), and if it served as a preheater for a fuel that WPS provided. An appointment was then made.

During the actual site visit, an inspector explained the program to the owners, asked a series of demographic and customer satisfaction questions, and finally conducted a detailed inspection of the SDHW system. Simple repairs would be performed if possible. More detailed repairs, if needed, would be made at a second visit.

Almost immediately PES found it difficult to locate the SDHW systems. Customers, for instance, would report they had a SDHW system and PES would instead find a solar space heating system. As we later discovered, over 32% of all solar systems are now owned by someone other than the original purchaser. This forced PES to visit the site of every solar system located in order find the SDHW systems. This course of action turned out to have significant positive effects.

Figure 1: Schematic of a typical active solar water heating system

Surprising Survey Results

As Table 1 shows, 53 of the solar heating systems inspected were specifically for domestic water heating, and 89 were for combination water heating/space heating systems. About 64% of the systems were found to be working. However, about half of the working systems needed some sort of repair or tune-up. About 85% of the original purchasers reported they made the investment in order to save money. Of those with working systems, 91% were satisfied with their system performance, while 50% of owners of non-working systems were satisfied!

Failed Pumps and Controllers

Failures typically consisted of a failed pump or controller. Because of the nature of SDHW systems as preheaters, a significant number of owners had no idea if their system was functioning or not. This problem occurred because installers failed to educate owners on how their system operated and in the simple observations they could make to ensure it was working properly. PES quickly found that failed systems could be easily repaired for only a few hundred dollars. We thus concluded that what had started as a survey program would be a much more cost-effective DSM program than a new installation program would be. In fact, the "Orphan" program was able to supply most of the DSM savings of a new installation program for 25%-50% of the cost.

WPS projected offering $1,400 rebates for newly installed SDHW systems, yet the same amount of energy could be captured from an "Orphan" program for from only $350 to $650 for a complete repair.

It also became evident that the Orphan Solar program did an excellent job of laying the foundations for a "new installation" program. Since the installer infrastructure had completely collapsed in Wisconsin, skills had degenerated, equipment was no longer coming to the state, and solar's reputation was bad. These were issues WPS wrestled with for its new install program. The Orphan Solar Program corrected all these problems.

The program retrained people. In fact, PES personnel soon became experts due to the variety of system designs and components they encountered. The program also put repair trucks on the road with a complete stock of parts to handle most existing systems. The Orphan Solar program became everything we would have expected of a new installation program, except we didn't have to install new collector panels.

Air-Based Systems are Easier to Repair

In all, 35% of the systems were found to be not working, and another 31% needed some tune-up work. A higher percentage of air-based systems were operating properly than were liquid-based systems. Air-based systems heat air and use blowers and ducts to move heat through the system, while liquid-based systems heat water or an antifreeze solution and use pumps and pipes to move the heat.

Air-based system failures were also easier and cheaper to repair. Failed blowers and leaky ducts required less labor to replace and repair than did failed pumps in a liquid-based system. PES found about 56% of the combination water/space heating systems were air based. The majority of Wisconsin's conventional heating systems are forced air, which allows an easier connection if an air-based solar system is used. Ducting an air-based system into forced air ductwork requires fewer and cheaper parts than does running a heat exchanger loop and pump off a water heat storage tank and into the existing ductwork. However, water heating performance is sacrificed. Most air-based systems were operating correctly, though in a few instances blowers or controllers had failed.

The liquid-based systems were mostly active, pressurized, glycol (antifreeze solution) based systems. These systems rely on the antifreeze to protect the collectors from freezing up and creating damage at night. Pressure is needed to keep the air that is inherently mixed in the solution from coming out of suspension and creating air bubbles. We found that freeze protection was good, but 56% of the working systems needed to be repressurized. An alternative to pressurized systems is to use simple water in a "drainback" system, where each night the water is drained from the collectors into a holding tank to prevent collector freezing. Drainback systems were found 18% of the time.

Pump failures caused 23% of the system failures for liquid-based systems. Pump failure is usually caused by pockets of air in systems which lead to pressure loss. These pumps are self-lubricating and when a large enough air pocket forms and reaches the pump, it quits circulating fluid, looses lubrication and eventually burns out. Air pockets are typically caused by either poor installation practices or leaks in the plumbing.

Air mixes with the circulating fluid when the system is first installed. An automatic air vent (AAV) should be installed at the highest point in the system to bleed off this air as it escapes from the fluid during its first few weeks of alternately heating and cooling. The system is initially over-pressurized to account for this drop in fluid volume. An expansion tank is used in the system to handle the normal change in pressure caused by heating and cooling the fluid.

After a few weeks of operation, the majority of undissolved air has escaped from the fluid and the AAV should be shut. The correct practice is for the installer to return to the installation after it has operated for a few weeks, and isolate the AAV to prevent depressurization. If this isolation is neglected, high stagnation temperatures cause the fluid in the collectors to boil out through the vent. This drops fluid volume further so that, when the system cools down at night, the system pressure drops to the point that dissolved air can come out of the fluid. This air eventually collects into an air pocket which moves through the system and ultimately reaches the pump, interrupts the fluid circulation, and causes the pump to burn out. This would not occur if the AAV continued to operate properly. But PES found most AAV's were blocked open by solder flux. PES located only one system that had developed a leak.

PES found that 21% of the controllers had failed. (Controllers are used to measure the temperature difference between the collector and the storage tank, and turn on the pump when energy can be collected.) We believe that 1990s vintage electronics have a longer life than 1980s vintage units and that this problem will decline in frequency.

Approximately 76% of the systems were roof-mounted and almost all had storage systems located in a basement. Due to roof mounting, shading of collectors remains low with 77% having no shading, and average shading being about 5%.

PES found that 33% of the systems had some sort of previous service work. About 45% of this service work was to replace failed pumps. Only a few controllers had been replaced.

To our amazement, 9% of all systems--22% of the SDHW-only systems--had been disconnected by their owners. PES found that approximately 33% of the systems are now owned by someone other than the original purchaser. The new owners did not have a good understanding of how their systems worked, so they disconnected them. We included these units in the "not-operating" category, even though no piece of equipment actually failed. These "new" owners were happy to have someone finally explain how their system worked.

Repairs

Repair work consisted of replacing failed parts. For both failed and disconnected systems, the system needed to be drained, flushed, and recharged. The glycol solution turned into sludge after repeated high stagnation temperatures. While the cost of repair parts averaged only $100, the average repair took a staggering 28 hours due to the large amount of time needed to flush out the clogged systems. This flushing consisted of simply continually pumping clean water through the system in order to force out the sludge that had accumulated.

Collectors themselves were found to be in good condition. Some yellowing of glazing had occurred, but there was no noticeable delamination or breakdown of insulation. About 54% of the collectors were 4' x 8's and the remainder were a variety of sizes.

Don't Junk that Collector

Solar heating systems have survived well in Wisconsin, and if maintained correctly, should continue to supply cost-effective energy well into the future. Air systems require the least amount of repair, while pumps and controllers cause the most failures in liquid-based systems. In many instances, this is because the original installers failed to ensure that the systems maintained charge pressure. Faulty pumps were responsible for 22% of the "hot water only" system failures and 25% of the combination system failures. Controllers caused 22% of the hot water only system failures and 50% of the combination system failures. Nine percent of the systems were shut off by new owners who did not understand how their systems worked.

Failed systems can usually be quickly put back into service. Some continual system maintenance is required.

To ensure long-term system performance, take the following precautions

• Install the system correctly. This is not a trivial chore. Consensus on how this is done for all the different system types is only now becoming clear.
• Conduct a follow-up visit to ensure proper operation and to isolate automatic air vents on liquid systems.
• Educate system owners. Knowledgeable owners can notify service representatives when system charge pressure drops to zero or pumps and blowers do not operate during sunny days as expected.

These simple measures should allow solar heating systems to produce long-term energy savings.

Jeff DeLaune is a research and development consultant in the marketing department of Wisconsin Public Service Corporation in Green Bay, Wisconsin. Chip Bircher is a demand-side management public planner with Wisconsin Public Service. Richard Lane is the owner and manager of Public Energy Systems, also in Green Bay.