Integrated Distributed Solar

Every building standing today is a solar collector. The primary collecting surface is the roof and if the building sits in the bright sunlight it will literally catch some rays. But even in this time of increased awareness about renewable solar energy to help reduce greenhouse gases and shift away from fossil fuels, most of that energy goes to waste.

With energy costs varying wildly and much of the world's petroleum held hostage overseas, the move to put underutilized rooftops to work has begun in earnest. Renewable solar designs are proliferating at a rapid pace. The use of rooftop panels to heat hot water is becoming more commonplace. Governments are discovering ways to encourage the use of distributed solar technology as a way to encourage diversification and drive down unit manufacturing costs. This has resulted in a rapidly improving economic model for distributed solar, with cost recovery now projected to occur between 2008 and 2010, fully 5 years ahead of projections.

The most cost effective way to gather this rooftop energy is to do it right the first time - when a building is built. Yet many buildings are undergoing modifications such as repair, retrofit or re-roof. So there are perfect opportunities to bring efficient, multiple benefit cost-effective solutions to problems of expensive heating and cooling or electric energy by rethinking rooftop energy capture and utilization.

What is the most effective approach for optimizing rooftop energy collection and minimizing a building's energy cost? It is by integrating different cost effective solar design elements. Nowadays, for example, collector surfaces can generate photovoltaic (PV) electricity and heat water for use in the same rooftop collector array. These exterior applications can be combined with designs that optimize availability of interior natural light, or that circulate rooftop heated air & water to drive space conditioning systems or support commercial or industrial operations such as laundries, crop drying processes, or even treatment of municipal sewage.

A century ago, sawtooth roof designs for low profile, 'big box' type buildings were popular. Before the time of cheap fossil fuels, these designs provided plentiful interior lighting to support cloth dying, rope making or other labor intensive industries. These designs make sense again today, where interior lighting can be as much as half of a building's energy demand. Using modern space framing technology, it is possible to build a sawtooth design incorporating rooftop PV electricity and solar thermal capability with energy efficient daylighting, solar driven space conditioning or process air. This means that as many as five energy intensive building needs can be addressed with a single ultra-efficient rooftop design. Applying this kind of structurally integrated solar roofing system can reduce overall building energy demand by half. In terms of building asset management this represents an optimum solution to the problem of unpredictable utility costs.

By integrating renewable energy (RE) with energy efficient (EE) systems, building owner-managers can expect to rapidly reconfigure their operating & maintenance budgets. They can also expect building users, whether employees or shoppers, to respond well to the natural lighting conditions offered by a sawtooth design. This means additional business economies tied to happy employees (reducing costs) and comfortable shoppers (increasing sales).

But there are still other reasons to invest in a sawtooth solar roof. Those reasons have to do with state & federal policy preferences for sustainability and energy efficiency. The California Global Warming Solutions Act mandates reduction in greenhouse gas emissions by 20 percent before 2020. The California Public Utilities Commission has established an identical goal, as well as a Zero Net Energy (ZNE) growth goal by 2050. These goals were reaffirmed by the Governor's Executive Order S-14-08, calling on retail sellers of electricity such as PG&E or SCE to satisfy 33 percent of their load demand with renewable energy by 2020. The multiple benefits of integrated solar roofing systems will help Californians meet or exceed these goals.

In fact, all three initiatives look to the state's major energy companies to become key RE/EE solution providers. In the renewable energy arena, SCE has led the way by campaigning to install PV on up to a million square feet of commercial and industrial rooftop space. Other utilities (SMUD, LADWP, SEMPRA) are implementing programs aimed at energy efficiency, while PG&E seems to be looking at both RE/EE solutions.

Whether the emphasis is renewable energy or energy efficiency, the economics of integrated, distributed rooftop solar energy make sense. Drawing on yesterday's wisdom as well as modern engineering & manufacturing know how, low profile commercial & industrial buildings can become part of today's movement towards cost effective, socially responsible enterprise.