Solar in a deregulated power market

Moustafa YoussefBlog

solar affect power prices merit order

Alberta has a market for the supply of wholesale electricity. Prices vary with supply and demand. All other provinces but Ontario have a utility that is responsible for generating as well as delivering electricity and maintaining its infrastructure. In Alberta these tasks are the business of private generators (e.g. TransAlta, Enmax Energy) and wires owners (e.g Altalink, Fortis, Enmax Power), and there is an independent body mandated by Alberta Utilities Commission, called the Alberta Electric System Operator, that manages the grid and price of power. In this blog post we’ll go over how power prices are determined, and how solar and renewables in general affect a deregulated power market.

Alberta has an energy-only power market, which means that generators only collect revenue from generating electrical energy. The price of wholesale electricity  is determined in real time by a merit order as shown below. Much like with any supply-demand curve, prices (y axis) are put in ascending order alongside respective generator capacity (x axis), and the point to which the supply and demand curves intersect determines the clearing/market price and clearing capacity. This happens every minute ensuring that demand is always met and consumers are getting the lowest cost for electrical energy. Generators on the left of the intersection point will be dispatched because their offering price is less than what the market established. For example a natural gas power plant can put up 30MW for $15/MWh from 3pm to 4pm. If at 2:59pm the price of power happens to be higher then it will be dispatched.

solar deregulated power market merit order

Renewable generators have no fuel costs and therefore can afford to sell power at any rate. If they are generating power they want it to be sold immediately. Therefore they will always be the cheapest generators on the supply curve. On the other hand fossil fired generators such as coal and natural gas have considerable operating costs and will bid their capacity at a rate that’s economically sustainable. Baseload generators will be operating for most of the time and will be found more towards the left and centre of the curve while peaker plants as their name suggests are only dispatched when market prices occasionally spike.

Supply demand curves are not new. The genius of this system however is that it uses price signals to balance a highly sophisticated circuit in real-time. Generation-demand have to always be in balance otherwise power quality will deteriorate or worse cause power outages which are expensive and just unacceptable.  Unlike a potato market where you get to meet potato farmers, look over a variety of potatoes or even consider substitutes, electricity is critical and its delivery must be anonymous and unconditional – power is transmitted to a pool/grid that everybody draws from. Electrons are electrons are electrons.

Like other energy commodities, consumption is independent of price. We flick switches, cook dinner, warm our homes whenever we need. System operators such as AESO rely on forecasting techniques to predict demand to ensure the system is prepared to meet demand both in real-time, as well as short and long term well being of the system.

Let’s take an example. Let’s say we have a grid that has a total of 250MW of generation assets – 100MW of solar, 50MW of coal and 100MW of gas, and their respective asking prices are $0/MWh, $30/MWh and $40/MWh. Let’s say that the demand is 100MW and the solar farm is generating 80% of its capacity or 80MW. Based on the generators’ merit order, 80MW of solar and 20MW of coal will be dispatched. Because coal is the last generator to be dispatched, the market price will equal its bidding price of $30, which all cleared generators will receive.

solar deregulated power market merit order

Merit order with 100MW of demand, 80MW of solar and 20MW of coal

Although the solar generator is willing to dispatch power for as low as $0/MWh, they receive the clearing price of $30/MWh. The owners of the solar farm will generate revenue of (80MW x $30/MWh) $2400 for every hour the system is dispatched. The gas generator will be standing reserve because its asking price is higher than the clearing price. If demand were to grow by 20MW, the coal generator will increase its dispatch by 20MW to make up for it. If demand were to increase beyond 130MW the gas generator will fire up and the clearing price will be $40/MWh, and then all three generators will receive $40/MWh.

Let’s suppose it’s getting darker and the solar farm is only putting out 20MW but demand is still at 100MW.  The supply curve will be shorter because the solar farm is generating less power. The dispatchable coal and gas generators will now have to increase their output by 80MW. As can be seen below this causes the market price to increase to signal to the natural gas generator to dispatch their power. Although the solar generator is supplying less power, they are receiving it at a higher rate because the clearing price is higher – same goes for the coal power plant.

Merit order with 100MW of demand, 80MW of solar and 20MW of coal. Clearing price is now $40/MWh

How does solar affect a deregulated power market?

As we saw above, renewable generation facilities are always dispatched because of their low marginal costs and they will accept whatever the market price is, hence they’re sometimes referred to as price takers. However as solar and wind capacities increase so does their synchronized impact on the clearing price. For example, in Alberta we sometimes notice how times of high wind can cause the price of power to drop. Wind generators are starting to act more and more like price setters. Large utility generators such as Calgary’s Shepard combined cycle natural gas plant also behave as price setter because of the considerable space they occupy on the left side of the curve. If you go to ets.aeso.ca to monitor the grid’s load and clearing price, you can sometimes see how an expected shutdown of a large dispatched generator can cause the price of power to spike. In Alberta, the clearing price can be as high as $999.99/MWh, and as low as $0/MWh.

Example of a merit order showing different marginal costs

Example of a merit order showing different marginal costs

From energy-only market to energy and capacity markets

The Alberta power market has been in the news for the past couple of months as the province gears up for its plans to phase out coal by 2030 with renewables and natural gas. Some called into question whether Alberta’s energy-only power market will be able to attract needed investments in generation given the historic low power prices. Generators have been enjoying relatively high prices in the past which seemed to be a sufficient signal to build more capacity, but now that there is a glut of electricity AESO has recommended to introduce capacity payments which means that on-top of the revenue made on selling energy, generators will also collect revenue for being available.

Beyond South: lower installed costs with east-west facing solar panels

Moustafa YoussefBlog

In the northern hemisphere the sun travels from east to west in a southernly direction and so aligning solar panels towards south allows them to capture the most amount of sunlight over the course of a day and year than any other direction. However because east-west facing solar panels are pointing in two different directions they allow for designs with lower installed costs.

As shown below, solar modules pointing east and west peak before and after solar noon. More energy is produced as the sun rises in the sky, increases in intensity, and points closer in the direction of a solar panel. So for example a five kilowatt solar array facing south at a low tilt can peak around 4.8kW by 1pm, but a 5kW array facing south-east (45 degrees to the east of south) might peak by 1130am and a south west array by 3pm.

east and west solar arrays peak before and after south arrays

east and west solar arrays peak before and after south arrays

The point being is that a single south facing solar array will peak once but an input composed of two solar arrays facing east and west will peak twice or at least make the peak a lot wider than with south facing arrays. Knowing that both solar arrays are not going to peak simultaneously means that we may be able to add more input capacity to the inverter, allowing it to operate closer to its rated capacity and enhancing its efficiency.

more solar panels east-west solar arrays

combined east-west solar arrays can improve the capacity factor of a solar pv system because they stretch the peak ofproduction

The design advantage of east-west facing solar arrays

The outputs of east and west solar arrays allow for a more stable power output. The higher the tilts and the further from south the more bipolar their total daily output becomes. Flatter solar panels peak closer together because their direction is closer to the sun’s travel path.

effect of east-west facing solar arrays on output

solar production of east and west facing solar arrays with different tilts

 

Feel free to contact us to learn more about the potential of your east or west facing roofs.

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.