HPSE Green Technology & Practices

Photovoltaics

Photovoltaics (often abbreviated "PV" and more commonly known as solar panels) are devices which convert sunlight into electricity. Solar panels have benefited from continually falling prices since the 1970's. In most locations, if properly installed, they can add from 10kW to 60kW to the schools power supply. Their initial cost can generally be considered "paid back" within 5-10 years. Many states offer rebates on system design and purchasing costs which would reduce this payback period. Please check your state page for more information.

Biomass

Biomass heating systems come in many different forms, but generally they convert wood chips into heat, usually through steam generation. Much of the wood used is a byproduct of timber harvesting, so wood which would otherwise go to waste can be used as a replacement for heating oil or electric heat. Vermont has a program which encourages biomass installation at schools.

Wind Power

Wind power is generated through large turbines in windy locations. If sited suitably, they can supply anywhere from 500 watts to 20kW. They are generally considered to be environmentally friendly in both construction and use, and their payback times are similar to PV arrays (5-10 years).

Day Lighting

Daylighting is not one technology, but instead a collection of design features in a building which combine to lower energy costs and increase the indoor environmental quality of a room. The building is aligned in such a way that exposure of its rooms to sunlight is maximized. Windows generally have high light transmittance (meaning they allow lots of light in) and cover much of the wall surface. Additionally, louvres, or light shelves, are placed outside the building. These reflect light further into the room allowing daylight to penetrate further into a room than it naturally would. The last technique to maximize daylight in a room is to install skylights. All of these techniques combine to allow high quality light into a classroom during daytime hours, and to allow the school to reduce energy costs.

Water Efficiency

Water efficiency is achieved by a school through a combination of policies and technology implementations. Exterior water use can be reduced by minimizing exotic species in the landscaping (which generally use more water than is available naturally). A separate gray water tank can be installed to minimize the expense of any irrigation water which is used. Indoors, low-flow fixtures can be installed throughout the school at a minimal additional cost.

Life Cycle Costing

Life Cycle Costing is an analysis of not just the initial cost of a product, but an analysis of all of the costs it will incur over its lifetime, i.e. the cost to own vs. the cost to buy. A relevant example would be compact fluorescent light bulbs (CFLs): Let's take a current estimate and say that incandescent bulbs cost $1 a bulb and CFLs are $5 apiece. Additionally, we will consider that the average CFL might last 8 years, while the incandescent may last 1. The last factor is the energy cost per year. Current CFL's meant to replace 100W incandescents are 23W. Each year the bulbs will be on for 500 hours a year. With this information we can figure out that replacing the incandescent 8 times and paying for more energy use costs us $68, and using the longer-life CFL will only cost us $18 over the same 8 year span.

Life cycle costing can be applied to products such as light bulbs and flooring, but also is a valid technique to discuss entire schools as a whole. An authoritative study regarding life cycle costing of schools was written by Greg Kats in 2006 and is available here: Kats 2006 National Cost-Benefit Study