Getting PV modules from the ground to the roof can be a back-breaking job. Modules that are being installed on sloped roofs are usually raised one at a time and then fastened to support rails, making installations slow and tedious. For small residential systems on low roofs, a typical method of conveying modules to a rooftop is to push them a short distance up a ladder to someone waiting above, but this method is impractical and unsafe. Mechanized lifts can be rented, but rates can be expensive enough to push a DIYer’s budget over the edge.
To remedy this problem, I developed an inexpensive and simple means to transfer modules to the roof. It can be built in a few hours by anyone who has basic construction skills, and materials cost between $45 and $80. (Although I used scrap strut pieces, strut can be purchased in 10-foot lengths from most home improvement stores.)
The lift is constructed of common building materials—lumber, pulleys, and rope—available at hardware stores. As designed, it collapses to less than 9 feet for easy transport and storage. The concept can be adapted to most module-hoisting needs.
The lift consists of two parts—the framework to which the module is secured and the top-of-ladder pulley support. The lift uses the mechanical advantage of two simple pulleys, rated for 100 pounds each, and relies on simple physics. With the pulley system, the force needed to lift a PV module is half the module’s weight. A 180- to 200-watt module typically weighs 40 to 50 pounds, so the force needed to lift the module will be 20 to 25 pounds.
The framework resembles a simple ladder, with a pulley attached at the top of the wooden frame. The wooden framework slides along the outside of the extension ladder’s rails. However, with extension ladders, the upper section usually sits above the lower section, creating a barrier to sliding modules smoothly up the ladder. Solving this problem is as simple as rotating the ladder 180° from front to back, which then permits the transition from the lower to upper section to become a landing.
The size of the framework depends on the size of modules being lifted. The lift we built can handle a single module up to 47 inches wide and 66 inches long. A protruding wooden lip at the frame’s base secures the module against the framework. At the top of the frame, a 1-inch-wide canvas strap holds the module in place as it is lifted to the roof.
The upper pulley support was made from strut and strut fittings as shown, but other means to support the pulley at the top of the ladder are possible. Strut fittings are connected with 3/8-inch bolts and standard strut cone nuts or springnuts. The pulley support at the top of the wooden support frame is attached to a scrap of 3/4-inch plywood, which is stronger than most dimensional lumber.
The ladder is first set against the roof eave. Next, the upper pulley support is placed on top of the ladder and the rope tied on the eyebolt adjacent to the pulley. (Note: Be sure to use an appropriate knot that will not self-release under any circumstance.) The wooden support frame is then placed on the ladder; the rope is placed through the pulley on the support, routed back to the upper pulley, and then extended behind the ladder to the ground. The module is set behind the wooden lip at the base of the frame and then secured at the top by the canvas strap. One person is on the ground, securing and hoisting modules, while the rooftop person removes the module from the frame after it arrives at the top.
Once the module is lifted to the roof and removed from the frame, the frame is lowered back to the ground. During lowering, the transition between the two ladder sections becomes a barrier. The rope normally used to raise and lower the ladder sections can be used by the person raising the modules to lift the wooden frame over the ladder transition. Using the ropes to pull the bottom of the support rack is easy when the rack is coming down empty.
Ken Gardner (ken at gardnerengineering.net) owns and operates a design-build renewable energy company in Ogden, Utah. He is a master electrician, civil engineer, land surveyor, and structural engineer who is NABCEP-certified. He is an instructor for Solar Energy International and teaches PV and hydro-electric classes.