Renewable Energy Options for
Renovations to the electric wiring and system in a Federal facility offer several renewable energy options. The primary renewable energy technologies related to electrical design are daylighting and photovoltaics (PV) as well as the overall design of the electrical system to allow for renewable energy integration. However, energy efficiency measures can also play an important role in electrical renovations.
If electrical upgrades allow for more advanced controls in the facility, daylighting may become a feasible option in the renovation. Particularly, the ability to control artificial lighting based on ambient light conditions is necessary for successful daylighting design. The renovation team should consider the potential for daylighting in the planning stage; any lighting upgrades should be designed in close concert with the electrical design.
Electric renovations should be integrated with any electricity-producing renewable technologies. By far the most common to be integrated with a building is a PV system that produces solar electricity. Besides the PV modules and mounting systems, the remainder of the PV system design is electrical.
Electrical renovations should accommodate the conduit and wiring needed to access the PV system as well as integrating components such as the inverter (which converts DC power to AC), other electrical components and emergency disconnects. Often, the PV modules will be located on the roof, but they can also be used in awnings, the building façade, or parking structures—each of these will require different electrical layouts.
It is important to ensure that the electrical design for a photovoltaic system is handled by PV experts. But, the PV system and facility electrical renovations should be designed in close consultation to facilitate solar PV system interconnection to the building's electrical infrastructure, to reduce costs and to maximize system performance.
Typically, inverters used in a "grid-connected" renewable power system (one that can feed power to and from a utility grid) are designed to shutoff the system when the utility grid loses power. This is intended to protect the grid and utility workers by ensuring that no power is fed back into the utility system. Systems also include manual disconnects for emergency personnel.
However, when a facility has a need for back-up or emergency power, the electrical design can be altered to accommodate this need and take additional advantage of on-site electrical generation. An on-site renewable power system can be coupled with batteries to provide on-site emergency power for a portion of the facility. If integrating PV into an emergency back-up system, consider putting the critical loads on a separate subpanel to enable those loads to be covered during emergencies. Integrating PV with emergency back-up should be considered from the early stages of electrical design. While this can sometimes improve the economics of an on-site renewable power system, it will alter the system sizing, design, and cost.
More information on grid-connected PV systems with storage is available in Section 2.2 of the Sandia National Laboratory report Distributed Photovoltaic Systems Design and Technology Requirements.
An example of using PV systems for emergency power is the State of Florida's addition of PV to its emergency shelters as reported by the Florida Solar Energy Center.
If the renovation will not include renewable technologies immediately, the electrical design should integrate the future needs of those technologies to simplify the addition of them later.
In electrical design, this could include adding conduit or a dedicated electrical chase to the roof or other external site for future PV. The electrical area should have adequate room for future inverters and other system electrical components and for the system to integrate into the electrical infrastructure. For example, the panel box should be rated to handle the needs of a PV system including enough available circuits and breakers for a future system. Ideally, these allowances will be labeled and documentation left onsite to prevent these components from being used for other purposes down the road.
In addition to daylighting and PV, if the facility has or will utilize any other renewable electrical technologies, such as wind power, then placement of interconnection points to the utility and other electrical design external to the building envelope should be considered with a view to the needs of those technologies.
In addition to considering renewable energy technologies, electrical renovations should incorporate energy efficiency and sustainable principles. According to the Los Alamos National Laboratory (LANL), building electric power systems can be made more efficient when they use:
- Higher voltage distribution systems in the building where allowable by code
- High efficiency or premium transformers sized to match the actual load
- High efficiency motors.
In addition, good design of the building's energy management control systems is important to take advantage of energy saving control strategies. Further details are available in Chapter 5 of the LANL Sustainable Design Guide.