Tappan Zee Bridge Solar Farm?

In today's Journal News, Greg Clary's column points out that some knowledgeable folks think recycling the Tappan Zee Bridge as a bike-ped crossing has some real merit. Last week's column looked into the options. So this week, let's go further.

Governor Cuomo thinks the option of the old TZB as bike-ped crossing is “an exciting option.” Erik Kulleseid, executive director of The Alliance for New York State Parks, thinks so too. Dan Biederman, who helped New York City successfully privatize Bryant Park as an economic driver for Midtown, agrees. 

But how would the state pay for maintaining the old bridge, if it recycled it for human-powered transportation? 

The state could bankroll the avoided demolition cost–an estimated $150 million–as a future maintenance fund. But there is another option. 

Why not privatize the air space over the TZB’s south-facing railing? Doing so would allow the state to lease that space for a public benefit in a public private partnership.

In other words, why not install a row of solar panels below the south-facing railing over the full length of the old bridge? That face has excellent solar exposure.

A quick calculation shows that the TZB solar farm will produce about electricity worth about $4.4 million in 2013. Three miles of solar panels could be installed for just over half what the cost of demolition would be.

That solar electric output becomes more valuable over the life of the system, typically 20 to 25 years.

At that volume in both annual dollars and kilowatt-hours, a TZB solar farm would be quite viable for a private organization to fund. Such a group’s business model could entail selling the power to the Bridge Authority under a low cost, long-term contract (aka a “power purchase agreement”).

In fact, with a few technical adjustments, both the new and old bridges could be lit at night by solar power harvested during the day. The sun could run the new bridge’s tollbooths as well.

We could have the first fully net zero energy bridges in the nation.

Or maybe the Town of Greenburgh or another orgranization would want to buy that power and lock in a 20-year price for electricity that will be lower than what we pay now to either ConEdison or New York Power Authority.

Technical notes: These calculations (by Croton Energy Group) assume a solar electric system using conventional photovoltaic modules (aka solar panels) with an output of 260 watts each. At a conservative average width per moduleincluding racking of 44 inches , three miles of bridge railing accommodates 4,320 modules. This solar array yields 22 million kilowatt-hours (kWh) in year 1. At an electric rate of about 20 cents per kWh–less than we pay now as residential ConEd customers in Westchester County–this output is worth about $4.4 million in year 1. Electric rates have been going up about 4 to 5% per year. By year 25 this annual output will be worth just under $20 million. Using current construction prices per photovoltaic watt installed (design, permits, insurance, labor, and all materials with some economies of scale gained from such a large system), the total installation price is roughly $85 million. The full installation of 4,320 modules with racking and wiring would weigh about 76 pound per module or about 50 tons per mile. During rush hour now, the old TZB holds up about 230,000 tons per mile in vehicle weight alone. Roughly, the new solar system will weight one half of one percent of the old bridge's vehicle traffic. So the solar farm is unlikely to present any weight challenges to the old bridge.