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BrightSource: Power Tower Solar Field Technology Innovations for Optimization and Cost Reduction

Report from CSPPLAZA: “solar field technology is vitally crucial to the performance of CSP plant which will directly influence the costs and benefits of overall CSP plant.” Recently, Joseph Desmond, SVP of BrightSource attended China International CSP station conference & CSPPLAZA 2016 annual conference (CPC2016) and made a speech themed as Power Tower Solar Field Technology Innovations for Optimization and Cost Reduction which has attracted many CSP attendees’ attention.The below content is Joseph Desmond’s speech in the event and it is organized by the video and stenography. For your detail understanding,  please read by the reference of speech presentation.

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Good morning, very nice to address here again. So, yesterday I had an opportunity to focus on lessons learned with special experiences on Ivanpah project. My topic today is power tower solar field technology and innovations for optimization and cost reduction. And in my speech, we focus on the next generation technologies which have been formed by our experience certainly in Ivanpah but also all the projects we have been working on. So, the topic today, I’ll elaborate here, are solar field layout software we have used and talk about something upgraded features, and describe lower cost heliostat design, a lot of talking about the solar field integrated control system and the expert system. I’ll go to detail about the wireless solar field network, a lot of discuss in receiver coatings and then finally I’ll talk about molten salt receiver and our Solar Energy Demonstration.

Solar Field Layout Software –Upgraded Version

Often time, I believe this is one of the most overlooked characteristics, I should say overlooked elements of good solar field design. And that’s the ability to work with existing landscape. So, what we find is our software with flexible heliostat placement that allows us to work within existing terrain while maximizing energy output. We also have the ability within the solar field to create “do not disturb” zones to avoid sensitive habitat or pre-existing structures that must be avoided during construction and during operation. The software can accommodate terrain with different slopes. In the case of Ivanpah, we have accommodated slopes about 6% grading.

If you then look at the challenges we’ve presented with, for Ashalim, you can see we’re using this optimization algorithm to determine the placement of heliostat. And this is a type of software that actually allows us to use irregular site because often time, it’s not possible to find a symmetrical layout. So, in this sense, we were provided with this land identified by the government and made it work. So, it is this software that allows us to do this optimization. We also know that in the software we are able to track tens of millions of components right from drive all the way from construction and operation for tracking. So, they provide critical degree view of all elements inside the solar field. What you see here is an example of Ivanpah where although we may not appear, we create driving zones. So, we anticipate the maintenance requirement that is accomplished by heliostats to a vertical position to allow small vehicles and cleaning equipment into the field. Of course, there are many benefits. Looking at this in the benefits of optimization, really are around that receiver here is seen what appeared to be a flat surface. So, the receiver is looking north at noon and it’s important to know all the optimization is done from the perspective of the receiver’s viewpoint. Although, you saw space in previous slide of the driving zones, this is what receiver looks like if you standing in top of tower and look at north. So why do we do this? Here is a view from south in the afternoon. That’s because after optimized solar field, we obtained 10~15 percent more energy per square meter.

Lower cost heliostat design

Now, we talked a lot about the benefits of lower cost heliostat design. This is second item on the agenda that I identified. What we want here is minimum steel loading. We want installation that are required in the site grading. So, you know that is a natural terrain. We didn’t grade and level. And those heliostats were placed exactly two meters into the ground and we have a GPS across the top. And we know the X,Y Z coordinate. We use that information into the part of software. We will talk about in a little moment.

Given the distances to the tower which you can see in the back, we actually have different category focal lens, depending on the distance, such as 1000 meters, 500 meters or 250 meters. And that focal lens provide great precision that you will see how to use it just a moment. Now, we have been a lot talk about industry design of heliostats there is different viewpoint. And in the right corner, you see the Ivanpah heliostat consisting of 2 mirrors, mounted in the back. Do you also see space there? And I enjoy showing you the differences between this technology and our next generation. But what I want to say here the goal is to strike a balance between optical efficiency and solar field cost including maintenance, because heliostats require maintenance with that equipment or the communications unit or other power connections, a large unit. Here we can access this from the ground which is considerably less expensive than the required very top equipment that sometimes, you can get stuck. So, the maintenance of solar field is critical. Given the heliostat is too small, as you hear yesterday, sometimes will be too many drive systems and many controllers required. And likewise larger heliostats require more expensive structural work. Heliostat design also impacts the construction time as well as the ongoing operation and maintenance.

As you hear with 15.2 square meters and just for reference that in Ivanpah, each heliostat provides 2.2 Kw of energy and almost for one California home on average one year. So, this is important in the heliostat installation. These pictures look in scale in the final report to see how they are. So, we develop this, here you see the pylons. They put them into the ground using a low-impact “ pylon driver”. And this process eliminates the need for foundations and concrete pads. So, their design to operate and preserve their structural integrity is for at least 30 years, but importantly, this process promotes natural draining and avoids corrosion, lets me explain why. In the background, you see a mountain. Although, Ivanpah is in the desert. It does get rain frequently. When the rain comes down from the mountain, washing across the flat area down the 60 degree slope I mentioned. It can be quite fast. When we were in construction for 3 months, we had a 17 years’ flood which means the mountain rains that came down with flooding which would be expected once in 17 years. So, in fact, the pylons are designed to withstand after a lot of a meter of soil around the bottom. They still maintained the structural integrity. On the benefits of this approach, they minimize grading and leveling with saving money. We maximize the retention of vegetation and natural features. Let’s me explain why. That’s also important. You heard yesterday concerns about the reflectactivity with the questions. I think I was asked at the end of presentation. By retaining the natural vegetation, you minimize the potential for dust since the corrosion soil remains the vegetation holds that in place. So, we see less dust from the Ivanpah, because we are maintaining as much as possible the national contours. although where we put the post of tower, we used to lay down area exactly. When we put this, we have this drilling hole and we vibrate the loosened soil, then vibrate down. Each hole is exactly 2 meters’ dig from the ground. That’s why you see, heliostat can have different heights as you look at them. But there are always 2 meters into the ground. The loosened soil is in place. We have this equipment pick up another tool, then insert pylons. And at this case, we vibrate down with a vibro-hammer. So, in the whole place, we have some stabilizing fin to keep them from moving. And here no concrete was needed, because the vibration packs the soil tightly around the finned pylon.

So, for Ashalim, this technique is different, because we find that we always have to optimize to adapt for local soil conditions. So in Ashalim, we also have much solution for soil to adapt for the desert environment. So, here you can see what that’s look like in this picture. Here is Ashalim, you can see the heliostat design has eliminated the space. This is actually four glass panels. This new design has fewer components which means easier assembly. So, this is different, less expensive and stronger, lower cost and easier to install. It is 25% larger than Ivanpah heliostat or is 4 x 5.2 meters. The new design what we operate now allows full freedom 360 degree positioning and is also self-powered. Again, topography is maintained here. You can see the pylons, here is Ashalim, during the construction. You can see the water, but again, the pylons were designed to withstand the occasional rain or snow. That’s what we find out in desert in Israel.

SFINCS and Expert System

The third elementary is SFINCS or solar field integrated control system and expert system. Speaking of SFINCS, because the job is to manage the distribution of energy across the surface of solar receiver and it is using real-time heliostat aiming and closed-loop feedback. Inside the solar field, we have on site weather systems. We have visual and infrared cameras that provide real-time feedback into advanced algorithms for solar field management. We also have proprietary optimization and control software. They have maximized projects’ performance and power production efficiencies. And also that you know is expert system which analyzes data in real – time and then provides recommendations for SFINCS and control operator about what steps you want to consider in faces of changing conditions. That’s could be weather or that could be movement of cloud cover or other system there designed to help our benefit the operator to make sure of continuous optimized production.

Here is a picture of Ivanpah solar receiver steam generator, consisting of 3 components. Each section, we had a center steam generator. We are providing one 600 Kw per square meter for the steam generator in the middle. On the top is the superheater and the superheater is maintaining 300Kw per square meter and the bottom is a reheater which maintains 150Kw per square meter which all of those has responsibility to each meter of designed heliostat that are individually controlled. I would note that the reheater has been eliminated in Ashalim design, because we learn there is no longer necessary. We simply have core steam generator there which works quite well.

Now, let me show you what’s that looks like of SPINCS. What you see here is solar boiler management system and infrared performance. We can look at in the middle on yellow. I mention it’s a cross section. You can see in the bottom of the Flux, kw per square meter and picture on the right is an example of one of weather stations on the data collecting. And that information is presented to us in local and center control room. Maybe for a little, more detail.

This is how we use laser scans. When using laser in both initial calibration and continued calibration, the GPS is used in positioning. So, we have coordinated field of heliostat which delivers flux to the receiver, enabling the system to achieve required steam temperature and pressure levels. That I mentioned the SFINCS software enables automatically continuing with calibration with those heliostats when not tracking mode. This is one of ways which we maintain the performance of the system.

Wireless Solar Field Network

This is a view of these receiver that we had in our SEDC facility. This is a different design, but you have a sense of the performing here which is an image just looking at focus on how it monitors the real-time continuing with optimization and we talk about two coating technologies just a moment.

So, talk a little bit about the wireless solar field network. In the right hand side, you can see the power and the power cable is communication cables that were lay across the solar field. Here we have the tower in the back. I give you a sense of challenge on how we could do the cost. We have put in place now the wireless solar field network. And that optimization is first in our Ashalim project. So, here is in Ashalim, we have 50600 heliostats. Their position is in just over a 3.15 square kilometers field. That’s communicated wirelessly with the SFINCS and that wireless system enables us reduce cabling by 85% in the solar field and that has benefited both reducing the cost and accelerating the construction schedule. If you look at the down below of the right, you can see the access point of solar field. So, in group of each cell, there is an access point connected with automatic control, but all these heliostats are controlled wirelessly. On here, this is a PV panel and heliostat wireless control that connected with super-capacitor to provide power. And this represents the first deployment of the technology that was tested independently and validated at SEDC which is a solar energy development center which is a fully operational “ sun to steam “ solar facility we used to test equipment, materials, and procedures as well as construction and operating methods.

Receiver coatings

This is a receiver coating in Ivanpah. These coating enables us do two things. One is to actually increase our overall performance, because it works more efficiently. Secondly, the frequency when you might be expected to recoat on the tubes, goes from two or three years to eight or ten years. This is an another way trying to find ways in squeezing cost down in the system.

This tower, by the way, was 140 meters which is one meter taller than the great pyramid in Egypt. When I show you Ashalim tower, you see that’s a 240 meters tall. So, it’s different design. But, these coatings is in three sections I mentioned the receiver, super-heater, reheater and temperature is in excess of 538 Celcius (1000F) , 160 Bar (2300 psi). On top of these projects, there is a tune mass damper which is serious with the shift, because in California, their concerns is not earthquakes, because the structure is very safe, but rather wind loading that occurs at the top. So, thinking of planning that, which is a engineering challenge.

Molten Salt Receiver at SEDC

This is just at the SEDC we are showing the molten salt receiver. We have molten salt storage tanks. This is in operation for about a year and half. So, we continue to make sure we fully understand its performance before we introduce it to the market, but it has been qualified in a bid in South Africa. We are hoping that we hear something sometime earlier soon about molten salt to be in project with 9 hours in storage. We actually would make to match proper technology to climate conditions. In the case of China, I believe the first configuration is hybrid which is a steam receiver with molten salt and heat ex changer on the tanks. We anticipate over time we may transition to molten salt again. When you financing the project, it’s important to take incremental risk and prove the value of each project you demonstrate and to manage the program. Let’s show you a couple of pictures here. First, talk about the Ashalim project which is 120MW. It has 25 years’ PPA and the land is 3.15 square kilometers. There are over 50 thousand new designed heliostats, version 2.4. It has just over one million surface area. Tower high is 240 meters. This project doesn’t allow for the natural gas. Natural gas here is used to maintain system temperature pressure’s over 9 so that we can see a very rapid start-up. For example, Ivanpah, it went from initial start-up that we took a couple of hours to learn the system to today we are delivering energy to the grid within 20-25 minutes to start-up. So quickly we can do that by maintaining it. I also pointed out that the use of natural gas is functional equivalent of driving the electricity from the grid for heat tracing to keep the pipes warm. That’s not unusual. Where you have access to gas, this is expensive, and if you can produce power from that, if it is allowed, it means better asset utilization which means lower cost and benefit. So, where it’s allowed to make sense and we try to design for it properly for the rules in those market.

So here show you a little more close, you can see here a tower on construction. The government made it available as is. When I say as is, this location was previously used for military training and target practice. So, one of the first thing we have to do when we have this plot was to check for and make sure all of unexploded elimination was clear for the site. We also have that in California project and it was for tank training for WWW II. So, it seemed sometimes you will be surprised with what you might find even in a desert. Once there we have done a couple of interesting features here. If you look a little closer, you see a tower, is being constructed that will be moved over into the foundation as it is completed, very slowly. But, there is also a river which runs through the property and we also have several historical trees that have to be protected. The software allows us to accommodate to work to these constrains which are pretty typical and another benefit is we can develop projects in area otherwise may be overlooked occasional rain that will require something different. We think that’s what we benefit.

The reason why we are here talking about technology is because we are a technology company. Solutions are available through our joint venture with Shanghai Electricity. So we encourage people who have interest in our technology to talk to Yvonne Huang, head of China business.

Yesterday I mentioned the guide book and you can download it for free. 124 pages. It talks about the value of CSP.

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