Fire-resistance of solar panels on wooden roofs

solar-modules-fire-roof-topThe fire-resistance of solar panels on wooden roofs is a frequently raised question by property owners and authorities in charge of the building permits.

One point to be addressed is the possible increase of the flammability of the roof and its effects on the safety of the building. Another concern is about the exposure to the risk of electrical shocks on first responders in case of fire on a building with solar panels on the roof-top.

We have checked the international safety standards, the testing procedures and discussed the subject with constructors and installers, in an effort to answer to the following questions:

1) Can solar panels trigger and transmit a fire?


Fire-testing – Source: TUV Rheinland

Solar panels from major manufacturers comply to the IEC 91730 standard. According to the IEC testing procedures any product matching the test is guaranteed as capable of [1] not inducing any fire if subject to fire close to its surface, [2] not transmitting fire in case of a burning material left on its top – as it might be the case of a blazing object blown by the wind – and [3] do not loose structural resistance during the test. Testing procedures from the TUV Germany are available here.

Another point is the fact that the only inflammable point of a solar panel is the junction box, which is made of uninflammable material, but it may host a flame triggered by electronics components, in case of a failure in the isolating material of the wiring connection. The worst that we have seen is that the PVC which the junction box is made of melts down, but the fire did never receive fuel enough to keep burning or to spread the ignition to the roof.

junction box burned | source:

junction box burned | source:

Our statistic (based on about eighty solar plants under maintenance service since 2008) shows that it happens in less than 0,001 % of the installed panels, and actually it happens soon after the installation and regardless of the installation mode – which let us believe that the cause is a defective production.

Indeed, as a junction box burns out, the DC circuit connecting the panels along a string opens up with two effects: to isolate the faulty panels from the other, and to stir an alert into the string monitor system (if there is one installed).

2) Can a solar panel increase the chance of flammability of a wooden roof?

There are two facts about fire: [1] fires go bottom-up (unless there are accelerants increasing the fire’s ignition point toward other directions); [2] fires require fuel, heat and air to keep burning.

[1] Solar panels are mounted on the top of the outer roof’s layer, so there’s no way the flames can spread underneath; the mounting structure is made of Aluminum and steel; cables and connectors are made of flame-retardant material. Even in case of strong winds from the panels’ side of the roof, the lack of consistent fuel in the back of the modules prevents the ignition of the roof’s outer layer and the timber beams underneath.

[2] The commonly used roofing system (clay tiles, tin roofs, asphalt built-in coverings) are made of original flame-retardant raw material. In any other case – as is the case of wood shingles – it is advisable to install a flame-resistant intermediate layer on top of the non-flame-retardant layer as additional safety.

Generally speaking, we can assume that solar panels do not add the fire-resistance risk of a wooden-roofed building, provided that the roofing cover has been correctly built of a commonly available flame-retardant material.

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Why open a Charging Station for Electric Vehicles

EV-charging-station-Frisco-USTo open a Charging Station for Electric Vehicles may be a good business opportunity, according to our simulation.

We’ve runned a draft model to simulate the economics of an EV recharging station deployed at an existing gas-station. The model assumes the electricity costs of Italy (Italy has among the highest cost in the EU).

The model considers the infrastructure costs required to set up two plugs connected to a 50 kW AC/DC station (DC for fast charge) and the operational costs connected to run the station 12 hours/day operator-assisted and 12 hours as a pure self-service.

To simplify the model it is considered the most popular EV on the market as the standard car (Nissan Leaf). By tuning the number of kWh delivered per day and the the local cost of the electricity, the models delivers the pay-back time of the investment.  Some of the features included in the investment could be added in a second phase to lower the start-up capital: the roof over the plugs, the fast-charge DC inverter.

The business would benefit from cross-selling services during the recharging time, taking between 30 minutes to 2 hours like refreshings from the local bar, additional car-services: car check-up, motor oil, car wash (internally).

Start-ups like the British ChargeMaster or the Dutch Fastned are already down to the network-deployment phase, and seem to confirm the realism about a similar business model.

The beckoning idea is that the major hindrance perceived by prospect EV buyers is the range – not price, not design, not the lack of a broad product line. Though the overnight charge allow the car for a minimum 120 km even in tough winter conditions, the fear of remaining stuck out of juice appears to being overcoming all the other advantages of an EV against a gas-fuelled car.

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How distributed storage, microgrids and renewables work together efficiently | by ILSR

Baseload-storage-graph-ILSR25-03-2014. A comprehenisve report [download here] from the ILSR (Institute for Local Self-Reliance) highlights the way distributed storage, microgrids and renewable generation can operate hand-in-hand to the benfit of customers, grid-utilities and the environment. Worth the downloading.

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How Microgrids are shaping their future. Right now.

Microgrid_2Microgrids are bound to become a considerable element in the energy landscape across the world.  Microgrids have been historically implemeted to power up remote sites and manage isolated grids or as a robust back-up generation source for mission-critical users. However the benefits from microgrids in the current energy landscape – as reported by a variety of pilot and commercial projects – have promptend big players to enter the market. In an interesting webinar from Greentechmedia   [here the pdf with slides show (12 Mb)] the Microgrid landscape and its operational benefits are discussed by experts.


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Nature’s article about the rechargeable revolution.

USA | The Nature-battery-status-2014US Joint Center for Energy Storage Research (JCESR) won a 150 M$ grant from the Department of Energy (DOE) targeting the research for batteries 5x denser in energy per kg and 5x cheaper than the current Li-ion batteries. And this by 2017. They must be sure that in the storage tech the rush for efficiency is all a matter of testing, which is the costly side of research. There are different storage technologies potentially suited to meet the target, but history tells us that not necessarily the early birds are the more successful. More money in the research would bring in more trials and more competition from around the world for what would be one of the biggest disruption in technology of the next years. To the benfit of the distributed generation and the off-grid systems. Read the interesting full article from Nature  >>here.

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Reducing Demand Power the new frontier for Energy Storage

demand-storageWhen looking at the bills, people have always been focusing their attention at the reduction of the energy part, the consumption ($/kWh).

But peak power charges applied by utilities ($/kW) gave been rising by by 10+% per year over the past 5 years in the US, according to an analysis by Green Charges Network. And now it accounts for up to 50% of the bill, especially for commercial customers with high peak-hour power demand.

In that case, a storage unit might serve non just as a mean to consume peak-hours the energy that you collected at off-peak time (over the grid or from own wind or solar plants), but also to shave off the demand peaks. This way you can reduce the > 15 min peaks above the service power you have contracted – which are very expensively charged by utilities – and reduce the contracted service power altogether.

Green Charges Network  claim they can even out the peaks, thus shaving a large part of those demand-charges from the bill, by coupling batteries with a smart controller fitted with stochastic data-mining sw application. They are able to offer the system on a service contract base to eliminate the upfront cost burden and to deliver pay-for-performance on demand reduction. The claim seemed convincing enough for receiving a grant from TIP Capital, an energy efficiency financing provider.

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Micro-grid 100% Renewables powers the German Village of Feldheim

Windpark_Feldheim_0876-7From the Rocky Mountain Institute blog.  Feldheim, a small town in the corner of rural eastern Germany, 40 miles south of Berlin, may be one of the best examples of decentralized self-sufficiency. Feldheim was a communist collective farm back when Germany was still divided into East and West. Now it is a model renewable energy village putting into practice how a micro-grid can operate while generating jobs and reducing the bills.

Thanks to a joint venture between the town and a local renewable energy investor (Energiequelle Gmbh) that invested in 74 MW of wind turbines and a 700 kW biogass plant, by 2009  the community was powered 100% with renewable sources from their own production. In 2010 the town residents detached from the national grid operator (E.on) and went on to become the first German city with its own independent micro-grid.

The power in excess is fed into the high-voltage grid as a regular power plant, but the energy fed into the micro-grid costs 30% less than the average electricity cost for residents in the surrounding areas.

Sure, this is possible also because the self-produced electricity is not burdened by grid costs and overheads spread among all other grid-connected consumers. However the experiment proves that a decentralised generation is not only possible but also  efficient and job-creating.

Read the original post >> here.

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Tesla Plan World’s Biggest Battery Factory

tesla-SThe Tesla CEO envisions “a plant that is heavily powered by renewables, wind and solar, and that has built into it the recycling capability for old battery packs.” According to a company’s newsletter of last week, the Tesla CEO envisions “a plant that is heavily powered by renewables, wind and solar, and that has built into it the recycling capability for old battery packs.” Tesla has a gigantic 85 kilowatt-hour battery pack, effective but expensive. But now, Tesla has is launching a plan to reduce cost through mass scale. And they have the – for now – secondary output market driven by the cousin company SolarCity, which is already integrating storage into its solar residential and commercial plants. Further info →  Greentech media.

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SolarCity DemandLogic | Is there any better way to show the benefit of batteries+photovoltaic system?

solarcity demandlogicSolar City program DemandLogic is campaigning the offer of free storage systems connected to residential solar plants to even the energy draw with the solar production, thus maximising the energy self-consumption. The program hits the base in tackling the uneven price increase for energy prices in the US for the last 15 years. The SolarCity program offers no upfront costs for the batteries, which account for the larger cost for storage systems (it doesn’t say about the battery chargers and system controller yet). The provider would charge the customer with a lease for 10 years. The customer benefits [1] from the reduced bill costs, [2] the reduced share of future tariff increases, and [3] the side-benefit of power-outages security. We would also add to that the saving of UPSs now almost all residential customers need to protect the expensive electronics we have at home.

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Off-grid inverters soon available with upgrade of grid-tied products

SolarMax PSome top tier string inverters manufacturers are ready to market upgrades of their grid products for off-grid mode operation.

At least for some manufacturers, this should come as a board to be plugged-in inside the case without the need to unload the inverter from the site. This is very good news, for the upgrade is rumored to come at a very low cost compared to existing island-mode inverters. The upgrades would be marketed as soon as the regulation about off-grid mode solar plants was defined in high prospect markets, like Italy.

The SMA Sunny Island 6.0H, for instance, comes a price tag around € 3.000,00  VAT excl. for installers. The product is specifically designed for off-grid applications and hosts lots of features like up-scaling flexibility, many custom configuration options and communication management. But for small residential plants who just look to increase their self-consumption amount the product is too much in terms of features and cost.

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