How Snow Impacts Solar Production in Alberta

Moustafa YoussefBlog

Snow Impacts Solar Production

A lot has been speculated about how snow impacts solar production in Alberta. In this blog post I’ll discuss the results of the effect of snow and tilt on the output of NAIT’s Solar Reference Array, which showed that snow incurred no more than 6% of loss on annual output.

Cold is good!

A 250W module (commonly referred to as a solar panel) or a 3kW array are going to produce said power under standard conditions which are a full sun intensity and a cell temperature of 25 degree Celsius (amongst other conditions). Higher operating temperatures lead to lower solar production and so lower operating temperatures lead to higher solar production.

This means that although solar panels receive less sunlight in the winter they produce more energy over the amount of sunlight they receive compared to warmer seasons of the year.

Production losses incurred by snow

The Northern Alberta Institute of Technology (NAIT) installed two solar sub-arrays facing south as shown below. One sub-array had its snow actively removed from it; the other sub-array was setup as the control and had no snow removed from it.

nait_array_solar_output

The NAIT Solar Reference Array which was built to study how snow impacts solar production in Alberta – The subarray on the left has snow actively removed from it, while the one on the right acts as a control.

A report was published after one year of observation and showed that losses incurred by snow are limited to a maximum of 6% of annual production. Below is a plot of  the array’s solar production and snow losses with increasing pitch. The angles mentioned in the report range from 14 degrees to 90 degrees.

How snow impacts solar production in Alberta

solar_production_snow_Alberta

How Snow Impacts Solar Production in Alberta

First of all it’s important to note that roofs that have pitches that are close to 12:12 experience the maximum annual solar output which is about 1,300 kilowatt-hours per kilowatt per year in Calgary, or 1,200 kWh per kW per year in Edmonton.  If your roof only has a slight pitch of say, 3:12 your annual production is only 15% less. Interesting snow had the biggest impact on flat pitched roofs, specifically the 18 degree tilt. Panels flatter than that suffered less from snow because they didn’t capture that much winter sunlight to begin with given how high up they are pointed in the sky.

It’s not a big deal how snow impacts solar production

Solar is a great resource in Alberta and cold temperatures in and of themselves are good for solar production. Whilst the impact of snow has a detrimental effect on a solar panel’s power production, it incurs no more than 6% in losses of total annual production. This is because we are so high up north that most of the solar production is concentrated between the months of March and September.

 

Decentralizing the Grid vs Disconnecting from the Grid

Moustafa YoussefBlog

decentralized_energy_infrastructure_solar

Many people that I talk to have a dream of living in an off-grid home powered by solar. Of ridding themselves of the utility meter, and paying no more bills.  This dream is easier than ever for homeowners to achieve since solar and electrical energy storage systems are now more accessible and affordable than they ever have been. But is going off the grid the key to a sustainable energy future where neighbours live independently from one another? Of course if you live in an area where running a power line to the local utility grid is prohibitively expensive then you have no choice but to setup an off-grid system. But is it practical to demand that every building meets its own energy requirements? In this post we will discuss the advantages of grid-tied solar and try to describe how a sustainable energy system might look like.

Grid-Tied Advantages

A grid-tied solar power system is one that is either directly or indirectly connected to the electricity grid. Grid-tied systems makes up 87% of the total Canadian solar market. In Alberta a solar micro-generation system is  connected to a building’s appliances, powering them first and exporting any excess to the local electricity grid, earning the micro-generator a credit on their bill.

Affordable and Flexible

An off-grid system can easily cost double the same size grid-tied system because of the added cost of the batteries. A grid-tied system is more flexible from day-to-day use, as well as in accommodating for seasonal variation. It can be of any size because the building’s appliances are still going to be connected to the grid and so will be able to draw power from it whenever solar power is in short of supply. The size of the system can be customized to suit a home’s available roof space and aesthetics and the owner’s budget and expectations.

Stored Energy vs Exported Energy

A grid-tied system exports any excess energy produced to the grid to do useful work elsewhere. This energy is transmitted to the local distribution system to do useful work on other appliances in the neighbourhood. On the other hand an off-grid system produces excess energy to be stored for when it isn’t available. The system has to meet the building’s power and energy requirements, meaning it has to deliver power even during the dimmest, snowiest time of the year. During the summer, the system languishes because it is so oversized; all that excess energy goes to waste because it has nowhere else to go. Furthermore, any mistakes like leaving the lights turned on could have a detrimental impact on the reserve of energy as well as the lifetime of the batteries.

Long Lasting and Maintenance Free

Tier 1 solar modules (commonly referred to as solar panels) are warrantied for up to 25 years. Together with inverters, they are proven to be a reliable and long-lasting technology.  Adding batteries to the system will only reduce its efficiency, and most will require routine check ups and can be hazardous if not maintained properly.

Decentralizing vs Disconnecting

It might be easy to discount from the importance of the electrical grid as it quietly transmits power across our heads and below our feet. According to the National Academy of Engineering it’s not the internet or the airplane but the electrical grid that is the greatest engineering achievement of the 20th century.

“Scores of times each day, with the merest flick of a finger, each one of us taps into vast sources of energy – deep veins of coal and great reservoirs of oil, sweeping winds and rushing waters, the hidden power of the atom and the radiance of the sun itself – all transformed into electricity, the workhorse of the modern world,” ~ National Academy of Engineering

What we need is not to disconnect from the grid, but rather to decentralize and diversify its resources. Essentially both concepts do the same thing – they bring energy closer to where it is needed. But rather than just making one building self-sufficient why not make whole communities self-sufficient?

Solar and wind are non-dispatchable sources of power, meaning they provide power only when their resource becomes available. A dispatchable source is one that provides energy on demand like biomass and hydro, and of course storage technologies including batteries. The role of the grid will remain pertinent, and there lies a place for batteries within it, but not in making one home or building sustainable but in supporting the operation and reliability of the local power grid. The electricity system was designed based on generation sources that were typically far from where electricity is needed, and therefore needed to be shipped long distances to consumers. The system is centralized in the sense that electricity flows from centres of generation to centres of consumption. As you can see below, a decentralized energy system can be made up of renewable generation and storage sources distributed where they are needed,  and of course would still require an electrical distribution system to connect these assets together.

decentralized_energy_infrastructure_solar

A neighbourhood that utilizes distributed solar generation and storage relies less on generation systems that are further away. Not all of the homes need to be equipped with solar and/or storage technologies.

Don’t Hate the Grid

A solar power system not connected to the grid is like a computer not connected to the internetanonymous wise person

It is much more economical, practical for community members to share their energy resources rather than to live independently from one another. The key to a renewable and sustainable energy future means integrating a variety of renewable energy systems that are specifically designed to meet the needs of a particular community, and for that there is certainly room for storage.

About the Author

Moustafa Youssef

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Moustafa Youssef P.Eng is the CEO of Neighbour Power. He manages a small team of engineers and installers that are ready to help you make a transition into a smarter and greener energy future.