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Feasibility Studies for Renewable Projects

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There is a lot of activity around adding renewable projects to isolated system and/or behind the meter. Renewable generation development has matured a lot in the last 10 years, and solar has come down in price to the point that the risk of installation is very low.

Graph published by IRENA from an Article titled: How Falling Costs Make Renewables a Cost-effective Investment

The yellow line is PV solar and the grey line is onshore wind. Its 2020 and PV Solar is on par with onshore wind for the first time on a kwh cost basis, below $0.05 USD/kwh. Offshore wind and CSP solar are dropping too but they are still closer to $0.1 USD/kwh, or double the price of PV and onshore wind.

Couple the high cost of energy in some markets with businesses with large cash reserves, developing behind-the-meter generation starts to be come very attractive.

Then there is the capital cost of storage predicted to be below $200 USD/kwh (for a 4h battery) by 2030, that is a 50% reduction from today.

NREL paper titled: Cost Projections for Utility-Scale Battery
Storage: 2020 Update

Coupling PV solar with storage could meet a signifcant amount of on-site energy requirements, below market rates. But before you can know if there is a fit for your site, you need a feasibility study.

What is a feasibility study

A feasibility study, in general helps a business determine if something can be done, and start to understand the risks of doing (or not doing) that thing.

The Merriam-Webster definition is simply, “a study to show if something can be done“, but I think for this type of project, Investopedia does a better job at the definition.

A feasibility study is an analysis that takes all of a project’s relevant factors into account—including economic, technical, legal, and scheduling considerations—to ascertain the likelihood of completing the project successfully. 

https://www.investopedia.com/terms/f/feasibility-study.asp

My role is typically to provide the technical and project management portions of the study, and provide inputs for the financial modelling and economic analysis.

Data Collection Planning
Getting the Planning Process Together

Technical Analysis for a Feasibility Study

Before I even get started with the technical analysis for a behind-the-meter project, I like to work with the client to determine the constraints for the project. If they haven’t thought about them yet, we workshop ideas until we agree on where the walls are for the project.

Some of the large items that we determine are things like.

How much energy do you want to dispatch?

Before even looking at the current load profile of the business I want to know how much of the energy they would like to displace. Are they aiming for a balance of lower cost self-generation and reliable utility connection? Or do they want to be net-zero so that they can generator 100% of their necessary energy?

System with Storage Integrated

To go further, do they want to be completely self-sufficient for periods of time, disconnecting from the grid completely. This is a microgrid type project.

We talk about these items even BEFORE we determine if there is a mechanism for selling/producing into the grid.

How much space do you have?

If this is a facility in a business park, there may be very limited amount of space to install PV cells let alone space for a wind turbine.

What is the timeline?

So, how fast do you want to deploy this project? If you want to go online within a year wind is out of the picture. Especially if it is going to be outside financed. The MET tower needs to be in the air longer than that just to understand the wind resource.

PV on the otherhand is much less capital intensive to get started, and if needed more can be easily added to the system. Install 1MW on year one and then another 500kW in year two and three, vs the upfront requirements of installing a single 2MW wind turbine.

Now lets look at the load

The first step for a project like this is to look at the load profile for the facility. Determine its shape, and “texture”. What you are trying to answer is:

  • Is it balanced throughout the year?
  • Is it balanced throughout the week?
  • Is it flat or “spiky”?
  • etc
Not a real load – from my home energy system

Then. depending on the answers and constraints to the project you can start digging in further. For example, if they want to reduce their utility load as much as practical, we want to see if there are ways to “shape” the load with the generation on site. This can be through automatic load shifting, manually through plant scheduling, etc.

To do this it is best to if the facility has a detailed energy management system broken into business or operating areas, with multiple years of historical 15min or better information.

As a side note, I wrote about this in a recent newsletter where I referenced a paper I was an author on titled “PLC BASED ENTERPRISE ENERGY MANAGEMENT SOLUTIONS” pdf here. I think its time that I update that paper with even easier to integrate solutions that have even more information. If that’s something you would be interested in let me know in the comments or on twitter.

Lets Evaluate some Technology

When I have a good understanding of the load profile and the most that would be able to be shaped, I start to look at various technologies and methods to meet the constraints of the project.

If the project goal is to be a 100% self-reliant microgrid for periods extending into DAYS, with full production/operation, then that technology mix will very likely include lots of generation and storage solutions including:

  • the main renewable resource (PV, wind, hydro, etc)
  • backup power, likely diesel or gas
  • chemical storage (Li storage, lead-acid, etc)
  • active demand side management and load shedding scenarios
  • etc.

This is where I start some very preliminary models with various technology mixes. When I have narrowed the combinations to something reasonable, no more than 5 and no less than 3, its time to have the first presentation.

These scenarios will have preliminary capital cost estimations and risk matrices associated with them. For example, people still feel very strongly about large wind which may cause risk from stakeholder feedback. Or there may be schedule/financial risk on the global lithium or silicon market that affects the cost or delivery of solar and storage.

Refine, Refine, Refine

At this point the team will have alignment on the various technology mixes and its time to refine the models and complete preliminary front end engineering and design for the scenarios.

There is a balance to refine enough to increase the confidence in the end results, but not so much that a lot of energy has been expended on dead end options.

To manage this I work with the owners after every iteration to ensure that they agree with the paths and decisions that I am making before they even see the report.

Time for some Project Management

In parallel with the technical feasibility portion of the project its time to start identifying capital costs, timelines, project risks, etc for the identified scenarios.

Data Collection Planning
Getting the Planning Process Together

This includes determining who the stakeholders are and if they are different for the various scenarios. Working with subject matter experts (SMEs) to determine permitting, testing, etc requirements for the options we are investigating.

I include detailed gantt charts and risk matrices with every study. They are easy to visualize the project and the critical path. In some cases the critical path for the project, and the risks that are out of the owners hand will determine the scenario chosen.

To pick on wind again, if there are onerous permitting requirements associated with wind, and the timelines are both long and not clear; then it may be prudent to chose an option that may have a higher levelized cost of energy (LCOE) but has a much lower set of risks.

Contrast to Isolated Systems

The process for isolated systems is very similar to behind-the-meter projects, the biggest different is integration and information from the system operator. If the project is placing a very large (compared to the system this could be 100kW) facility, the system operator will need to provide detailed information related to interconnection at the start of the project.

This isn’t a microgrid

The other consideration when connecting to a system that you don’t control is the power purchase agreement and the interconnection agreement (PPA and IA).

These agreements, and the path to obtaining these agreements, are an integral part of the feasibility study. If this type of project isn’t something that has been done before, there may be large schedule and expense risks related to the interconnection that are out of the owners control.

How important is a Feasibility Study?

Well, its critical to the predictable success to any project. For small or simple projects they are likely just done in your head, or as part of a standard project approval project. So, even if the project folder doesn’t contain a document titled “Feasibility Study: …” that doesn’t mean that the items identified in this article weren’t considered.

Opportunity for BTM and Isolated System Projects

With the LCOE for PV solar and onshore wind below $0.05 and the cost of battery storage dropping, there has never been a better time to invest in renewable/storage projects.

If you have any questions or want to discuss developing a feasibility study for your site, contact me today for a free consultation.

Updating Heating Control – Home Micro Grid

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This post is all about how I’m updating the current control of the ETS that we installed last November.

When it was installed we had the contractor do the least control they could to get going, with the plan that I would upgrade it in the winter. Well COVID happened and that sucked up all my time, so now is the time.

What is an ETS

But first, what is an ETS? I wrote a short post about ETS devices here.

The coles notes version, is that an Electric Thermal Storage unit is a device that you can convert electricity into heat and then store it to be released later. This allows us to load shift to the night when our electricity prices are lower.

What’s Installed Now

We have a Dimplex VFMQ 40 installed in the studio, this heats the entire studio in the winter. In the shoulder months it will heat the main floor too allowing us to minimize the heating in the rest of the house.

The contractor installed a programable thermostat that serves as a charge controller. To ensure that we charge the heater every night, regardless of the temperature of the room at 11pm when the rates decrease, we have it set for 28C starting at 11pm, 15C during the high rate time and 18C at the mid range time. This ensures that if it is extra cold out the heat will come on in the middle of the day when the rate is at the “normal” level.

The heat is released with a dial thermostat on the side of the unit that isn’t exactly accurate.

A “typical” February

Currently we heat the space to 24C during the evening and it “holds” for most of the day, and it will drop to around 19 and 20C by 6pm when I am leaving the office. This room temperature is based on the “dial” on the side of the heater. Its hard to dial in a specific, comfortable temperature.

Overlaying the power for the storage heater you can see how the current charge controller “charges” the bricks b/w 11pm and 7am.

There are a few things that I should be able to dial in with the new design, including limiting the swings. Ideally I would like to keep it b/w 22C and 18C, the snapshot above is b/w 24C and 17C.

What I want to have

The goal of this little project is to control the heater more efficiently and be able to modify the schedule from the Home Energy Management System.

As a starting point, I want to control the room temperature at 18C overnight, starting at 6pm in the evening, and then warm up to 21C during the day. The image above is from the members only video that will accompany this post.

I don’t have temperature sensors that I can plug directly into the controller, so, I’m going to re-use the programmable thermostat to control the room temperature and the controller will ONLY control the charging cycle for this version of the controller.

The goal is to limit the saw toothing and conserve as much energy as possible.

Added benefit in the shoulder season

In the shoulder season there isn’t as large of a heating requirement, and as such there isn’t as much of a need to “store” more heat energy than is needed.

So, if I keep track of how long the heater charges for, I will know how much energy was needed the previous day. Couple that with an understanding of the deviation from the programmed temperature, for example, if the goal temp at 5pm is 20C, and it dropped to 18C, or if at 10:50pm the temp is more than 1C from the goal temp, we can assume that the “tank is empty”.

But if the previous day didn’t use all the charge time AND the temperature at 10:50pm is above or at the goal temperature, then we can “just” charge the difference rather than over charge.

This is for the programming side, which I haven’t finished yet. First the hardware control.

The Control Circuit Now

The control circuit looks like this :

K1 is the charge controller, this is a programmable thermostat today. I will be re-using the thermostat for room temperature control, replacing the dial.

It is mounted next to the heater itself, so I will have to move it closer to the desks to have the desirable affect.

RTR is the room temperature controller. This is a dial on the heater today. This will be replaced with the thermostat when I replace the charge controller.

First Step: Hardware Design

I’m planning to use the ClickPLC as the controller for this part of the project, and will be adding everything to the VTScada application that I have monitoring the energy use at the house and studio.

The new additions to the control circuit as it stands today include:

Replacing the thermostat with a relay that will be energized from an output on the PLC. I was initially hoping that the PLC would be able to drive the contactor in the heater directly, it is 24Vdc rated, but looking at the thermostat I don’t think so.

The thermostat has a rating of 1A, where the PLC has a rating of 0.1A.

Click PLC output rating
Programmable Thermostat

Oh yeah, and one is AC and the other is DC. So a relay is definitely going to be needed, but it doesn’t have to be a big one like I assumed in the video.

I won’t be buying the new relay until I have the software started, and that is what I will be writing about next.

Also I have finally added the CTs to the generator panel and that means I can start sizing my emergency storage solution.

The load appears too small for what I was expecting, so I will have to do some investigating before I start planning how big the battery needs to be.

Looking for your help

And on that subject, if you know a company like BigBattery (but in Canada) who puts together systems like this one, let me know. This may be just what I need for my battery generator project as part of the home microgrid.

If you know of a supplier in Canada, let me know in the comments (if you’re a member) or email at jeffmackinnon@jmkengineering.com

Electric Thermal Storage

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There is a lot of talk about chemical based energy storage (batteries), but before batteries there was thermal storage.

Thermal storage is similar to using bricks or water for thermal mass, it limits the thermal swings by slowly releasing the thermal energy into the space even after the heat source (sun, fire, etc) has gone away.

Electric Thermal Storage (ETS) operates in a similar way. The ETS that we have installed in the studio used bricks to store the heat. When there is a call for heat in the space a fan draws air over the bricks “wicking” away the heat and releasing it in the space.

I’m not a mechanical engineer, so don’t quote me on these terms.

Current Electric Thermal Research

There is still a lot of development in ETS technology, even with the attention to battery storage.

Most of the products we see on the market today, that are ready to buy still use thermal mass storage, but there is really neat chemical storage options being developed, like from Neo Thermal where they store the heat in a salt, similar to the heating pads you put in gloves to keep your hands warm.

Other Research in ETS

I did a quick search for “thermal storage” on IEEExplore and saw a few really interesting papers, including a couple that looked at using chilled water for “cooling” storage in commercial buildings[1]. This was an old paper, but thinking about it, with the AC load in California lining up with solar power, this may be a great place to dump excess generation from wind or solar installations.

Building on that old paper is this one from 2016 – Use of Adaptive Thermal Storage System as Smart Load for Voltage Control and Demand Response [2].

In this paper they propose that a large scale ice thermal storage system, similar to the 1985 paper, could be used as part of a demand side management scheme for fast voltage control and load shaving.

Another paper spoke to the point that concrete waste from building demolition has a use as the thermal storage medium[3]. The specific heat measured in this paper ranged from 700 and 850 J/K*kg.

For comparison, the 176kg ETS that we have installed in the studio stores 32kWh and uses clay bricks that have a specific heat value b/w 900 and 1000 J/K*kg[4]. This recycled material may not be the best solution for small commercial applications, but possibly a solution for large industrial applications where there is more space and possibly a lot more waste heat.

So what?

If we are going to reduce our carbon emitions fast enough to limit the climate crisis to BAD, rather than great filter, then we will need to develop all the tools in parallel. There isn’t a silver bullet.

While chemical storage in batteries is one great way to electrify everything, thermal storage is a great tool for building energy management and helping the shift to distribute energy resources (DERS) like solar everywhere, and wind.

This is something that I put together in an afternoon of reading, imagine the possibilities if you spent your masters, or made engineering thermal storage solutions a winter project.

Citations

  1. D. R. Laybourn and V. A. Baclawski, “The Benefits of Thermal Energy Storage for Cooling Commercial Buildings,” in IEEE Power Engineering Review, vol. PER-5, no. 9, pp. 31-32, Sept. 1985, doi: 10.1109/MPER.1985.5526437.
  2. X. Luo, C. K. Lee, W. M. Ng, S. Yan, B. Chaudhuri and S. Y. R. Hui, “Use of Adaptive Thermal Storage System as Smart Load for Voltage Control and Demand Response,” in IEEE Transactions on Smart Grid, vol. 8, no. 3, pp. 1231-1241, May 2017, doi: 10.1109/TSG.2015.2513743.
  3. J. B. Martinkauppi, T. Syrjälä, A. Mäkiranta and E. Hiltunen, “Some Aspects of Recycling Concrete Crush for Thermal Heat Storage,” 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA), Paris, 2018, pp. 707-710, doi: 10.1109/ICRERA.2018.8566981.
  4. https://www.engineeringtoolbox.com/specific-heat-solids-d_154.html

What is the Point of Common Coupling

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I have been working with a couple regulated utilities over the last few years. Neither of these utilities have a lot of small independent power producers (IPPs). There may be a couple of edge cases, or medium sized wind farms, but as a rule they generate all the energy they need.

This isn’t a microgrid.

The grid is getting smarter

However, the times they are a changing, and while I was working on the mini-hydro project in Labrador I recognized that in some cases understanding the requirements at the point of common coupling (POCC) can determine how a project is going to develop.

An example of a “smarter” grid

A lot of the time it is way more interesting to put energy into the civil and mechanical aspects of a new project, we are building big things even if ther are small, but how the POCC is going to be controlled can determine a lot of what needs to be completed within the IPP facility.

This is where an interconnection agreement comes in. The role of the interconnection agreement is to ensure that the IPP is producing power in a way that doesn’t impact the customer power quality. It will have the limits of operation, how to synchronize, how the utility communicates that it can accept the energy, when the IPP has to be isolated at the POCC, etc.

There is a lot of protection and controls design that needed at the POCC. Settings need to be developed that will allow the system to synchronize to the utility, trip when there is a fault on either side, if the IPP can’t accept the entire load, ensure that it trips if the frequency dips, etc.

Without a detailed interconnection agreement the IPP risks not having the proper protection elements in place when it comes time to start operations and producing power. Then what happens?

The general requirements for interconnection protection are typically straightforward, they always include:

  • Over/Under Frequency Protection,
  • Over/Under Voltage Protection,
  • Sync Check across the protective device before energizing and
  • Overload and overcurrent protection in both directions.

The timing and details of these protection elements is where all the time is spent. The interconnection agreement will include a description of HOW the IPP resource will be deployed locally.

  • Is it an energy resource?
  • Is it a inertia resource?
  • Is it a reserve power resource?
  • etc…

If the resource is going to be a source of short circuit current during a fault on the system, then it shouldn’t have an instantaneous trip set too high such that it removes that short circuit current.

If the system is relatively “weak” in that area and a large motor starting drops the voltage for a short period of time it would be a bad time for the new generation to disconnect on low voltage.

Standardizing Interconnection P&C Design

We’ve started developing a standardized interconnection panel that includes all the necessary protection elements, SCADA connections, data concentration, etc. A system that allows IPPs and renewable resource developers to focus on areas that they are stronger in.

The system is still in preliminary design, and version one will include the following:

  • RTU/SCADA data concentrater to have all devices on site communicating to a single point
  • Multipurpose protection elements for MOST scenarios
  • GUI protection configuration
  • Cellular Network router/gateway

Including the technical abilities, it will include a full set of relay protection test sheets that will allow you to verify that the protection settings that you added do what they should.

If you are interested in a product like this and would like to help steer its feature set, send me an email at jeffmackinnon@jmkengineering.com

We live in a digital age, but that’s for computers – Newsletter

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This is a re-post of our weekly newsletter.

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