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Exploring solar at the Exploratorium

The Exploratorium, one of San Francisco’s major tourist attractions, now has a 1.3-MW solar power system on its roof. But installing the project involved some major challenges, including the use of a barge crane due to the Exploratorium’s waterfront s

By Paul MacDonald

Next time you're attending the Intersolar trade show and conference at the Moscone Center in San Francisco, and some solar power sightseeing is on your schedule, visit the Coit Tower where you can get a bird's-eye view of one of the highest profile solar projects in the city, on the roof of the Exploratorium, the city's renowned science museum.

You can see exactly how the 1.3-megawatt high-efficiency SunPower system on the Exploratorium's roof is performing by simply taking a walk down to Pier 15 at the Embarcadero waterfront area. In the Exploratorium's lobby is a display center that updates the solar array's performance every 15 minutes.

Thanks in part to the solar power system, the Exploratorium (one of San Francisco's more popular museums and a major tourist attraction) is now one of the world's greenest museums.

The Exploratorium's new home was built as part of a move from its longtime location at San Francisco's
Palace of Fine Arts. This $300 million investment into renovating Pier 15 on the Embarcadero waterfront area was designed to result in the largest net zero energy use museum in the U.S. with a cooling and heating system that uses bay water, in addition to the solar power facility. The 330,000-square-foot museum itself serves as an interactive exhibit, educating the public about energy-efficient design.

Del Monte Electric, one of northern California's leading electrical contractors, took on the challenge of building the solar project and installed nearly 6,000 PV solar panels on the roof of the building, succeeding under challenging and constrained site conditions and an accelerated construction timeline. The panels make up more than 78,000 square feet of the roof, or about 21,000 square feet more than the size of an NFL football field.

"Our biggest challenge was timing with the weather, water, and the barge crane that lifted a vast amount
of material to the Exploratorium roof," explained Vince Almason, general foreman at Del Monte Electric.

"Planning was critical to saving costs by scheduling only two lifts with the extremely expensive barge crane," Almason added. "We were successful in strategically getting the 30,000 feet of rail and 60,000 feet of wire lifted to the roof and installed before the second lift and installation of close to 6,000 PV panels."

The solar installation had an accelerated timeline, which also added to the challenges for Del Monte Electric, a veteran electrical subcontractor with 75 years of experience and a diverse portfolio of time-- sensitive projects under its belt. The company's pre-construction planning, scheduling, and organization proved critical to the project and crew, who had limited time and access to the roof during construction. The weather also proved to be an uncontrollable factor with a combination of heat, wind, and rough tides that all had to be considered during the two successful barge lifts.

"This was a landmark project for Del Monte Electric," said John Hunter, president of the company. "The capabilities of our team were continually challenged during this project as we met critical deadlines under aggressive schedules." Del Monte Electric's expertise in solar installation was the contributing factor in keeping the project on time and on budget, he said.

Scott Mullins, vice president of Del Monte Electric, explained that completing the Exploratorium project successfully was often about timing and keeping on top of details.


"We did not get involved until the project was mostly built," he said. "The buildings were roughed in, and most of the rough framing and electrical installation within was already done."

In effect, Del Monte Electric hit the ground running. "We started on site two weeks after we bid on the project," said Mullins.

It says a lot about the company's experience and resources that it was able to pull things together and get started on such a complicated project in such a short period of time.

Both SunPower and the general contractor on the new Exploratorium construction, Nibbi Brothers General Contractors, were helpful in coordinating the solar power portion of the project, Mullins said. "It was definitely a collaborative effort."

In terms of the challenge factor, the project was right up there with some of the other solar projects the company has taken on, said Mullins. One such project was a solar install for the Mt. Diablo Unified School District in suburban San Francisco, which involved 12 MW installed over 51 school sites.

"The Mt. Diablo project was challenging because we had so many different people over so many different sites at one time," said Mullins. "The challenge was rotating crews through so many different sites,
focusing on one activity."

The Mt. Diablo project involved installing a staggering 28,000 PV panels on carports and rooftops throughout the campuses and over 150 miles of wire. It was also done with SunPower.

"The Exploratorium project definitely also had its own unique set of circumstances that made it a major challenge," added Mullins.

And that challenge came in marine form, due to the waterfront site of the Exploratorium, which sits on San Francisco Bay. As noted, the solar modules, string wire, and rail all had to be delivered to the site by barge. Once the panels and associated materials were on the roof of the building, there wasn't a whole lot of space for storage.

"We had to figure out how to get all this equipment up there and get it stacked on the roof so it didn't affect the structure of the roof and didn't impede us from doing the actual solar project installation," said Mullins.

Staging materials adjacent to the building was not an option-there is only the water of the bay next to the building. For logistical reasons, they also had to be very careful about where the materials were placed on the roof. "If you were to put the materials in the wrong spot, you could basically paint yourself into a corner with the solar install."

The delivery of materials was staggered, but in a limited way since there were only two large barge deliveries.

"The first delivery was of all the rail, wiring, and the mounting hardware to get the panel supports in. We got that installed on the stanchions, and then we received all the PV panels on the second barge delivery.

"By the time we got the PV panels up there, all the rail was up. We could not set the PV panels over the roof-we had to basically spread the panels out as we received them, on the rail."

Among the challenges on the Exploratorium solar project was getting material for the project onto the roof using a barge crane. The first lift with the barge crane saw 30,000 feet of rail and 60,000 feet of wire lifted to the roof, and the second lift (right) brought close to 6,000 SunPower panels up to the roof. 

They had to carefully plan out the movement of all the pallets of panels to the roof, and laying out the panels over the rail. "There was a lot of work that went into that because you could not stack too much on one location of the rail. The crew had to spread it out all over the roof."

The barge-mounted crane was lifting the materials the equivalent of two to three stories. "What made that difficult was that as the tides changed, the ability for the crane to boom out also changed," explained Mullins. "The barge crane was not able to maneuver into some areas, so we ended up being limited to where we could be lifting materials on to the roof."

Del Monte Electric had met with the barge company, determined how much space the materials would take on the barge, and had planned the lifts all out. "We did all our due diligence on the front end," said Mullins. "But factors beyond our control-the tide-changed things.

"Initially, we thought we would be able to boom material into different areas and have all these landing areas. But with the tides, we had only a couple of landing areas, and we had to move a lot of material by hand. It made it much more difficult than our original plan."

Equipment was assembled at the different drop points on the roof, and crews spread out the material to the parts of the roof where it would be installed.

This was a classic case of how important it is to have the resources and experience to think on your feet in a situation; where what worked on paper all of a sudden did not work in practice, thanks to Mother Nature and the nature of tides. "We had to adapt, and our foreman on the project, Vince Almason, and the crew did exactly that," said Mullins.

They also had to deal, to a much more limited degree, with getting some materials delivered to the site by land. The Embarcadero and Fisherman's Wharf, which is down the way from the Exploratorium site, are two of the most heavy-traffic tourist areas in San Francisco.

"The project is located right on the water, but the Embarcadero walkway is at the front of the building,
and there is constant pedestrian traffic. With deliveries, we had a flagperson and a crew to get trucks in and out-we found that early mornings were the best time to do the deliveries."

Layer on top of all this activity a tight timeline. "They wanted it done in three months from start to finish, and we were able to meet that schedule," says Mullins.

With any solar power install, things have to be kept on track, but this tight timeline made that even more important.

"We were very diligent about our pre-task planning," says Mullins. "We did some mock-ups and good layout planning that allowed us to work with the schedule. We were able to keep the crew size consistent throughout, and we did not need a peak of manpower towards the end of the project."

SunPower supplied all the solar panels for the Exploratorium solar project. Inverters were supplied by Satcon, and the mounting system was from DPW Solar. The panels make up more than 78,000 square feet of the roof, or about 21,000 square feet more than the size of an NFL football field. 

They took an area of the roof to do the mock-ups. "The stanchions that supported the rail were installed by the roofing contractor before we got on site, so we needed to make sure the rail system leveled out in a way that the panels sat on them uniformly, so they were all on the same plane.

"We built a mock-up on one area of the roof and made sure it worked well, before we moved to other areas."

Mullins noted that with this solar project, they had a different order of tasks. "We kind of had to approach it backwards. Normally, you install rail, PV panels, and then wiring. With the Exploratorium project, we had to install the rail and then figure out where the panels were going to sit on the rail. And then pull all the string wiring before we set the panels because we wouldn't have been able to get the string wiring under the panels later.

"The mock-up allowed us to get an idea of how the panels would lay out for the string wire."

This being San Francisco, weather played a role in the project. "The wetness in the morning was a concern, because you'd get slippery conditions," said Mullins. At daily safety meetings, they discussed the slippery conditions and how best to deal with them.

"But the biggest concern was the wind," said Mullins.
This was also dealt with at the safety meetings. "It would kick up, and since we were exposed on the roof, we always had to make sure to tie down the pallets of PV panels."

They had literally hundreds of quick connect tie-downs so that as solar panels were being lifted off a pallet, a tie-down would quickly be put in place. This was another idea of foreman Vince Almason. "It worked really well," said Mullins. "When you cinched them down, they stayed tight, but they were easy to loosen up, so you could slip panels in and out. We didn't want any cardboard flying off into the bay."

As noted, SunPower supplied all the solar panels for the project. Inverters were supplied by Satcon, and the mounting system was from DPW Solar. Mullins praised the work of Todd Chambers, SunPower's construction manager, who helped throughout the project.

Del Monte Electric has been involved in a number of projects with SunPower, which is based in the Bay area's San Jose. Del Monte Electric, based southeast of San Francisco in Dublin, does most of its work in this region of California.

The company specializes in public and privately funded projects that require a high degree of electrical knowledge, have aggressive schedules, and require complex installations, which meant the Exploratorium project was right up their alley.

Del Monte Electric's successful track record includes projects ranging in size from $50,000 to over $10 million in electrical value, and its expertise covers solar installations, healthcare facilities, and educational institutions.

"The Exploratorium project was a good fit for us, and we felt very fortunate to be part of the team," said
Mullins. "We believe we had been a strong partner for SunPower on other projects and working closely with them, we were able to get the project done on time and on budget."

Currently, Del Monte Electric is working on a smaller project in the Berkeley area of San Francisco and is hoping to participate on some larger solar projects around the region.

The chances of more solar projects going ahead in the area are good. The San Francisco area is home to Silicon Valley and companies such as Google, who have made it clear that clean energy is a strong focus for their growing energy needs.

And, Mullins notes, there is a strong desire on the part of Del Monte Electric, and its employees, to be involved in more solar projects.

"It's exciting," he said. "I think most everyone who worked on the Exploratorium solar project felt they were contributing and doing something right for the environment-and that is gratifying."