[MUSIC] Now we're going to address generating energy from the sun, the second of the big two intermittent renewable energy sources along with wind, that many people see as critical components of the energy transition. People have been using the power of the sun for centuries. Building sun rooms and greenhouses to capture and contain warmth from the sun and building dwellings in South facing areas to make best use of available sunlight to warm living spaces. The ancestral Pueblo people inhabited cliff dwellings at Mesa Verde in Southwestern Colorado more than 800 years ago. Energy from the sun and shelter from the cliffs allowed them to inhabit this harsh environment year round. [MUSIC] While passive collection of heat in the design of buildings and greenhouses is still important, aggressive capture of solar energy to create electricity dominates the solar picture today. There are two primary methods of generating electricity from the sun, solar thermal and solar photovoltaic. Solar thermal electric generation systems collect and concentrate sunlight to produce high temperature heat to produce electricity. These are sometimes called concentrated solar power systems. They feature two main components, reflectors or mirrors arranged in a large field or array capture and focus sunlight onto a receiver. In most types of systems, a heat transfer fluid is heated and circulated in the receiver and used to produce steam. The steam is converted into mechanical energy and a turbine which powers a generator to produce electricity. To maximize efficiency, solar thermal power systems have tracking systems that keep sunlight focused onto the receiver throughout the day as the sun changes position in the sky. A photovoltaic or PV cell, commonly called a solar cell is a non mechanical device that converts sunlight directly into electricity. Sunlight is composed two photons or particles of solar energy. These photons contain varying amounts of energy that correspond to the different wavelengths of the solar spectrum. A PV cell is made of semiconductor material when photons strike a PV cell, they may reflect off the cell pass through it or be absorbed by the semiconductor material. Only the absorbed photons provide energy to generate electricity. When the semiconductor material absorbs enough energy from photons, electrons are dislodged from the semiconductors atoms. Special treatment of the semiconductor surface during manufacturing makes the front surface of the cell more receptive to the dislodged or free electrons so that the electrons naturally migrate to the surface of the cell. The movement of the electrons each carrying a negative charge towards the front surface of the cell creates an imbalance of electrical charge between the cells front and back surfaces. This imbalance in turn creates a voltage potential like the negative and positive terminals of a battery electrical conductors on the cell absorbed the electrons. When the conductors are connected in an electrical circuit to an external load, electricity flows in the circuit, the PV cell is the basic building block of a PV system. Individual cells can vary in size from about a half an inch to about 4" across. One cell produces 1 or 2 volts, which is only enough electricity for small uses such as for powering calculators or wristwatches. PV cells can be connected in a packaged weather type PV module or solar panel. Electricity generating capacity increases with the number of cells in the module or in the surface area of the module. PV modules can be connected in groups up to hundreds of modules to form a PV array. The number of PV modules connected in a PV array determines the total amount of electricity the array can generate. Photovoltaic cells generate direct current or DC electricity. Nearly all electricity and transmission and distribution systems is supplied as alternating current known as AC. Devices called inverters are used to convert the DC electricity to AC electricity. PV modules will produce the largest amount of electricity when they are directly facing the sun. Some arrays use tracking systems to maximize performance and we'll talk about these later in this lesson. The examples of solar PV and thermal generation we've looked at so far are built at the utility scale. That is, there are large scale generation facilities hooked to the electrical distribution grid and used at various locations where demand exists, such as in cities. However, solar energy is available and can be captured anywhere. Small installations designed to provide power primarily at the point of capture are referred to as distributed solar. The most common application of distributed solar is to install solar PV panels on an individual home or commercial building to generate electricity. Any extra electricity generated can be sold back to the district power grid if the system is set up to allow this. The Drake Landing Solar Community in Okotoks Alberta, just South of Calgary employs distributed solar strictly for heating. 798 solar plate collectors are mounted on four rows of garages. When the sun is shining, antifreeze is pumped through the collectors, heated and is moved to the energy center. Once there, the heated solution passes through a heat exchanger to heat water which is stored in short term thermal storage tanks. The hot water is distributed to heat households and the cooled water is returned to the energy center. When heat is not required, it is stored in a series of 35m deep boreholes for later distribution when required. [MUSIC] Solar photovoltaic energy is used exclusively to produce electricity. Large solar thermal facilities generate electricity as we have just shown. But smaller solar thermal setups can be used for smaller heat applications such as space and water heating together solar PV and thermal energy supply only a very small component of global energy demand. However, building from the almost zero in 1990 both solar PV and solar thermal energy supply have grown rapidly at annual array rates of 36.5% and 10.9% respectively through 2018, that rapid growth translates into a lot of electricity produced since 2007. Almost all in O. E. C. D. Countries and china which are able to accommodate intermittent solar output into already existing electrical grids. As we saw for wind power. We can harness solar energy only where the solar resource is sufficiently abundant to make make it worthwhile. In this map, the hotter colors yellows and reds show where solar input is relatively high and consistently available. These areas have a good solar energy resource base and are best suited for solar energy development. Solar energy is most available and most consistent year round in tropical to subtropical areas, particularly in dry areas where there is little cloud cover the low latitude deserts of africa, Asia, North America and Australia. Thus have the best solar resources, along with the high Andes of western south America wetter areas in India Southeast Asia Central Africa and south America receive less solar energy, particularly in the rainy season. At high latitudes. There's a significant solar resource available only in the summer months, with very little in the winter when the sun is very low and available for less than half of each day. We'll return to the solar resource map later in this lesson, when we talk about building a new solar facility. [MUSIC] Let's look at the positive attributes of solar as a source of energy. The lists of both positive and negative attributes are very similar to wind energy attributes. Greenhouse gas emissions from both solar photovoltaic and thermal solar are very low, assuming that substantial emissions associated with their construction average out over a long producing lifetime. As we just saw on the global map, solar energy resources are abundant in many areas of the world. Once built, solar facilities have relatively low operating costs as there's no need to purchase fuel. Long term data on repair, maintenance and panel replacement costs are still being gathered. Local applications of solar distributed solar generation are considerable. Many building owners have taken advantage of electricity savings gained through installing rooftop solar, but installation costs remain a challenge particularly for the average homeowner. In most cases, local solar site should be connected to the electrical grid so that they have back up when the sun isn't shining and can sell excess power to the grid when available. However, there will likely be additional costs associated with grid connection. Now let's look at negative attributes or challenges in using solar energy for electrical generation. A key issue is intermittency, as has been said countless times solar panels generate energy only when the sun is shining. Depending on where you are, the sun can be a reasonably predictable although intermittent resource, sunny low latitude areas or it can be a minor niche contributor at best in cloudy climates or at higher latitudes. This graph shows electricity generated from the whole solar farm in sunny southern Alberta for a week in late winter 2022. Compared to the window put chart we saw previously, this at least looks more regular, zero energy output at night of course. But on sunny days like March 21st and 22nd, the facility put out 20 megawatts or more of its 25 megawatt capacity for a full nine hours. But for the other four days recorded here, solar power production was very choppy even during the middle of the day as weather conditions were more variable. Again, as we saw for wind, a substantial amount of electricity is generated but in an intermittent and only partly predictable manner. Solar generation facilities are built where the solar resource is best. Solar power is generally not viable in Great Britain as its maritime climate and northerly latitude makes sunshine a rare resource during much of the year. However, the company X Links proposes to build a 1500 square kilometer solar, wind, battery power facility in the North African country of Morocco. And to transmit the power to Britain use 3800 kilometer long sub-C HVDC, which means high voltage direct current cable run in relatively shallow waters as shown on this map,. They forecast delivering 3.6 gigawatts of electricity for an average of 20 hours per day. Up to 8% of Great Britain's electrical demand or approximately 7 million homes. Will attribute to innovation and bold planning, costs will be huge to bring solar to the UK and many technical regulatory and financial challenges must be addressed if this project is to succeed. Solar panels require a lot of steel, concrete and high purity glass, also called polysilicon to build, plus strategic materials like copper. Polysilicon and copper in particular must be produced in far greater quantities in the future if we are to build a number of solar farms envisioned in rapid energy transition scenarios. We'll talk more about critical metals and supply chains in a future lesson. As the solar power industry matures, we have to address the safe disposal or recycling of solar panels and associated infrastructure. Particularly as the panels in early solar facilities are less robust and durable than current technologies. Recycling can be very expensive because of the diverse and exotic materials and solar panels as we saw in the last slide. But recycling will be necessary in order to maintain a supply of the rare earths and critical metals to manufacture new panels. While some obsolete panels go to landfills, that's not a viable long term solution. Utility scale solar generation requires huge land areas that are rendered unusable for other uses, such as conventional agriculture or ranching. Well, that may not be a big issue in wide open unsettled areas. It's a huge consideration in densely populated areas. Every major new project seems to attract objections and protests from affected stakeholders to people who just don't like that particular project or technology. This is particularly true for land intensive solar projects built near population centers or on prime agricultural acreage. It's important to remember that just because a project is deemed to be environmentally beneficial doesn't mean it will be seen as beneficial by everyone, particularly those who live next door. Let's welcome back Carl from Transalta Corporation who will talk about building utility scale solar generation. Hello everyone. Nice to join you again today we're going to discuss technical considerations for the sighting, technology selection and development of a solar photovoltaic power facility. Without further ado, let's dive in. One of the first considerations inciting a solar project is the resource assessment. We saw this map earlier. It shows the average solar energy intensity which we call G. H. I. Or global horizontal radiance around the globe. It represents the fuel available for your project. And while solar energy is free, it is limited. The solar resource is impacted not only by the sites distance from the equator latitude but by other factors as well. For example, cloud cover from a long rainy season can significantly reduce your solar resource. So we see better solar resource in the desert areas of the western United States compared to the relatively rainy Southeast as with weather. Solar energy will vary year to year. So in solar development we often refer to a typical meteorological year or T. M. Y, which is the historical average representation of what a location can expect. Once we've assessed the high level potential of a location, we must then consider more site specific details. The terrain profile should ideally be level east to west with the consistent slope towards the equator, south facing. If the project is in the northern hemisphere and north facing, if it is in the southern hemisphere, with this in mind, no site is perfect. Rolling terrain can however be optimized with some light civil engineering work or by accepting a solar array with a lower installation density as well as some shading production losses. Arrays can also be skewed east or west to favor morning or afternoon production respectively. The ground across the site needs to be stable so recently disturbed or swampy areas are to be avoided as well as areas that have a risk of frequent flooding. The far horizon profile is also an important sighting consideration. If the project is shaded by distant mountains or lies at the bottom of the valley, then the generation potential is going to be impacted. The two displayed sun path diagrams to pick two very different sites. The upper one on a flat prairie region and the bottom one. In a mountainous region. We can see the mountains can block a significant amount of generation potential. Similarly tall objects like trees, buildings or wind turbines can produce panel shading. Land cost is another important consideration. A solar takes up a large area footprint. Land around large urban centers can be very expensive. As is land used for high value crop production. So more rural land that is less agriculturally productive can often be acquired for less. Energy from a solar project makes its way to customers through the transmission system. A vast network of high voltage power lines and lower voltage distribution networks link generation to customers. Citing a project near sufficient transmission capacity is a critical consideration. Building transmission lines is very expensive. So the closer to a viable interconnection point, the better. Even if there is a nearby transmission line, the available capacity must be assessed as there is a limited amount of power that can flow through the wires similar to water in a pipe. Additionally, there may also be a queue of other generation projects looking to use that transmission capacity. So applying for interconnection to your system operator is critical as soon as your project is sufficiently developed. So we have a site with a great solar resource, cheap available land that is both relatively flat and obstruction free and there's nearby transmission capacity. What else do we need to consider? Well, we need to consider environmental concerns and set back requirements, which is the distance our project must be from particular environments and sensitive areas. The specifics will vary by region, but generally you will need to assess and mitigate concerns around sensitive and endangered species. Both plant and animal. Migratory birds, wrap turness, breeding grounds, areas with heritage significance and protected lands such as parks and nature preserves. Setbacks from water bodies and wetlands and setbacks from residences and roads. This map from the nature conservancy summarizes wildlife areas to consider in the Central United States. When citing a solar project, you may also need to perform noise and glare studies. You may wonder what makes noise at a solar farm? The DC to AC power inverters make an audible hum. This usually isn't an issue but if there is a nearby residence and the equipment is placed too close to the perimeter of the array, there might be a problem. Glare or light reflected off solar panels can be an issue for nearby major road intersections or residences. An assessment will take into account the solar racking technology used as well as the season and time of day to flag the severity of risks. Now that we've considered project citing issues, let's talk about technology options. The current preferred utility scale panel technology is by facial monocrystalline panels. They feature the highest energy conversion efficiency, capturing 20-22% of the solar energy and converting it to electricity. That by facial two ,sided configuration generates electricity from both direct light on the front side of the panel as well as from the indirect light reflected to the rear side. This adds 5 to 30% to a project's energy production. Historically polycrystalline panels competed with mono crystalline panels as a lower cost, lower performance product. However, manufacturing improvements have made polycrystalline panels obsolete. Thin film solar panels are the main competition to monocrystalline panels, they are less expensive since they require less silicone and energy input to manufacture. However, they are also notably less efficient, capturing approximately 12% versus 21% of the available solar energy. So more area and structural racking is needed to achieve an equivalent generation potential. In 2020, thin film solar had only 5% of the utility scale solar market share. However, technology improvements and increases into silicon is raw material price could lead to a dramatic increase. The structure that holds the solar panels in the array is referred to as racking. There are two primary racking options used in utility solar, fixed tilt and single axis tracking. Fixed tilt racking holds the panel at a fixed angle towards the equator. This is optimized for seasonal energy production. The racking spans east to west and can accommodate rougher terrain than single access trackers since there is no rotational access or drive mechanism. Since it is a static racking option with no moving parts, the initial cost and maintenance requirements are low. Fixed tilt tracking technology is still the preferred option for very high latitudes where 45 degrees tilt or higher is optimal. Or where there are many cloudy days that limit gains from daily tracking. Single access trackers are currently the racking technology of choice for utility scale installations driven by cost reductions and reliability increases in recent years. Based on 2020 data, for roughly an 8% increase in project cost, we can achieve a 15-35% gain in energy production. This is accomplished through daily tracking of the sun from east to west. The racking itself spans north to south and the structure rotates along the horizontal axis to provide the tracking motion. [MUSIC] The drawback of single access trackers comes from their horizontal axis of rotation, which provides 0° of tilt to the equator. This means that the further you get from the equator, the poorer their performance. There actually is a third tracking option ,dual access trackers. These track the sun both during the day and through the seasons to provide the very best utilization of your solar panels. Unfortunately, high installation and maintenance costs make dual access trackers uneconomic for utility installations, particularly as individual solar panels become less expensive. Just a few words about project economics as they are highly dependent on individual project and site. This graph is from a 2020 National Renewable Energy Laboratory report that compares installation costs for different sizes of fixed tilt and one access tracker installations. Key takeaways are, there are economies of scale in developing 100 megawatt versus a five megawatt project at 25% reduction in the cost per watt. The cost of the solar panels themselves is the single largest component, more than 40% at the 100 megawatt scale. Other plant materials like racking, foundations and electrical make up another 24% of the project cost. So the cost of your project can vary dramatically depending on the current cost of input commodities like silicon and metals. The timing of when you contract your supply is thus very important. Solar costs have been dropping rapidly over the decade from 2010 to 2020 ,fixed and tracking solar costs have dropped less than 1/5 of their starting cost. The challenge now will be to continue the downwards trend against diminishing returns and material supply chains. As well as to balance them with energy storage to provide a renewable energy resource that is paired with electricity demand. >> Carl, thanks for that excellent review of solar energy, project planning and construction. As we saw for win power, these are major industrial projects that require the talents and hard work of many people, from professional engineers and field workers to bankers. Now that we've studied hydro, wind and solar, let's move on to another form of energy generation, often regarded as renewable biomass and biofuels.
