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New inverter technology making solar energy more affordable

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It seems like such a simple solution to our energy problems. The sun, a 4.5 billion year-old source providing a seemingly endless supply of free radiation for solar energy production, without the extraction, refining or transportation costs or any of the associated harmful emissions. Solar Energy has been around for decades, yet it is only recently gained more mainstream acceptance and attention as a viable source for big-time utility companies.

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Green Energy- Clean and Silent

The biggest advantage of solar energy is that beyond the production of panels, there are zero associated emissions: no smoke, gas or any other chemical bi-products are associated in harvesting solar. Eliminating the destructive green-house gases responsible for destroying our atmosphere, the biggest winner is our planet. Once installed, beyond maintenance needs, there is no constant requirement for more raw materials (coal, oil, etc). It doesn’t require destructive extraction processes (mining, drilling), doesn’t need additional refinement procedures (more chemicals and environmental damage), nor does it produce the related emissions from transportation and distribution of the materials into its end-user form. Once active, a solar hybrid systems sits there and soaks up the energy used to offset overall grid-tied traditional energy usage or the self-sufficient off-grid solar and storage options.

If solar power is clean and free to make, what’s the hold up?

For years, the initial expense of setting up a solar array heavily outweighed the savings over cheaper, conventional sources. Solar energy systems were quite expensive to install/maintain, and their per kW savings not very enticing over conventional sources to offset that large initial investment. Early adopters saw a decade pass before the solar savings yielded offset that initial installation investment. The good news is that solar technology has made huge advancement in the past few years and continues to develop at a break-neck pace. Panel prices have dropped significantly in past years, cabling and other system costs continue to fall. Companies now develop products aimed at addressing the cost of solar energy, with the goal of allowing solar to be easily adopted by the mainstream: Power to the People.

Reducing costs of Solar installation by 75%

The US Solar Energy Industries Association (SEIA) reported that the cost of solar panels has dropped 60% in the past 3 years, also gaining more efficiency in their energy harvest capabilities. Analysis by the DOE showed installation labor to be largest expense category associated in PV by a factor of 2 to 3 over the panels framing and other associated expenses. A new solution was needed to bring down costs for residential and small/mid-sized commercial projects, that focus shifted attention to solar inverters.

Solar installation designers and engineers have traditionally had only two main options for converting DC to AC power: String Inverters or Micro Inverters. Both presented significantly different benefits and disadvantages for installers, with installation expenses varying up to 20% depending on the inverter selection. Both solutions had drawbacks: what one would gain in convenience, it would sacrifice in performance and maintenance. The development of a new class of inverter, the Micro Parallel inverter (MPI), combined the installation simplicity of a string inverter with the intelligence and energy harvest advantages of a micro inverter. The MPI inverts 4 panels in parallel and provides advanced data, communications and IT features to users. It is aimed at helping to further the proliferation of solar energy into the residential and small commercial market segments (5KW-200KW). The MPI can also be utilized for off-grid, grid-tied, and grid-tied with emergency backup applications. It has a wide enough input; voltage, current and frequency range to operate with generator or battery based grids.

Designed around the concept of easing the ergonomic burden of installation, activation, and maintenance, the MPI is able to reduce the cost of acquisition and ownership. Since MPI’s are a new technological innovation they benefit from additional features now available with the newest electronic controllers and communications modules. The result is; improved intelligence, ubiquitous data display with remote control, and energy harvest schemes that continuously adjust to maximize the harvest of energy from each panel.

Installation is simplified

Wiring for residential or commercial 240V AC single or 3 phases is similar to standard building construction. The new design incorporates a modular, plug-n-play approach. One inverter controls multiple 300W solar panels. The individual channel design (1 per panel) continuously optimizes the maximum Power Point Tracking (MPPT) for each panel. Combiner boxes, DC optimizers, and DC GFCI’s are eliminated by the AC design. The panels are mounted in 4.8KW clusters of 4 rows of 4 panels. The MPI’s can be mounted to a panel’s frame, the array racking, or directly to the roof. Panel inter-connectivity uses quick connect, DC terminals leading from the MPI to 4 solar panels. The MPI’s can handle a mix of panel technologies ranging from 100-300W. Each MPI is then quick-connected to a 240VAC 20A 4.8KW trunk cable. The trunk cables lead to a single disconnect (visible from each MPI) which is wired directly to the sites breaker panel. The trunk cabling supports 16 panels, with just one disconnect at the breaker, unlike the 16 separate disconnects incorporated into each micro inverters AC connector. This reduces cabling as well as installation and wiring time by 75%.

Maintenance savings

Maintenance savings come from the added monitoring features. The fault alert processing notifies users when a hard failure occurs, its location, and affected part for expedited ordering and replacement. These features will reduce unneeded maintenance truck rolls for just shaded or dirty paneling. Repairs and replacement visits become faster and more efficient by reducing trouble-shooting efforts, and allowing easy-access to in-field repairs. The unique channel design uses power sharing, allowing for graceful degradation and enhanced fault knowledge and channel to channel health and status communications. When Micro inverters fail, they lose this extra level of knowledge. Micro-parallel inverters remain operational with as few as 1 panel, on any channel generating DC power. String inverter architecture can lose generation from a string due to the shading of one single panel.

Installation, operation, and monitoring is controlled by the system’s Electricity Monitor and Control (EMC). This unit plugs into any AC receptacle near the breaker panel and connects to the site’s internet router or when internet is not available, directly to a computer via an Ethernet cable. The EMC has the ability to monitor 4x the number of panels compared to a micro-inverter architecture. Self-Mapping features map each inverter location to its physical location in the array in an automated setup. Installers simply close breakers, and correct faults detected during startup. This feature improves the accuracy of the map and eliminates the time-consuming and costly practice of hunting the field for erroneously mapped panels.

Better Efficiency in Energy Harvest

Some micro-parallel inverters also benefit from a new thermal survival feature that improves reliability, availability and energy harvest. TRC’s SmartPhase MPI offers a unique patented power output throttling circuit that protects their MPI against heat-related failures. It can be activated remotely or programmed to maximize energy harvest and prevent over generation when limits are imposed. This improved energy harvest increases the payoff associated with using oversized panels. This reduces costly losses of energy from panel overheat and failure, as well as ensures that limits are not exceeded. The strategies also ensure maximum efficiency of the system for the most energy harvest. Less downtime, less degradation means more energy and more efficiency of the field.

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