On Grid Solar Farm

Working with Electric Utilities

Balancing the Needs of PV Customers with Utilities

Solar contractors and solar customers often find themselves on the adversarial side of utilities when interconnecting PV systems to the electrical grid. Most of the time this is due to a lack of seeing the other’s side and/or understanding of the other’s position.

Let’s first look at the utility’s position regarding PV systems. Many utilities offer incentives or encourage their residential customers to have PV systems installed on their properties. The reason for this is almost always for the purpose of appeasing the wishes of their customers. This an effort of goodwill because they know that electrical customers like the idea of energy coming from a clean renewable source and most of them also like the idea of owning their own energy. The benefit to the utility is not financial unless the PV system energy reduces load demand during periods when the cost to generate that power from other sources is high.

With residential customers, those periods are mostly in the afternoon and evening and then again in the morning as the sun starts to rise. This being the case, the PV systems with smart energy storage are the only systems that could financially benefit the utility as well as the owner of the system. They store the energy produced during the middle of the day and then feed it into the home and grid during the peak load periods.

With commercial customers the situation is different. The peak load period may be during the normal business hors of the day or 24 hours a day. These customers with PV systems may be shaving loads throughout the day or they may need to shift loads to a time of day other than the solar hours of the day. For the utility to benefit financially, a load demand study must be made for the specific customer. These customers with PV systems will also need energy storage for load shifting, peak load demand reduction and to provide consistent load support during climatic events that vary frequently during the day. The truth is that PV systems without smart energy storage do not save the utility money.

The exception to this would be with smart inverter technology that is controlled by the utility. California and Hawaii are both working through this process and it will become a more universal option in the very near future. However, these smart inverters and smart energy storage systems don’t address another issue for the utility. They understand how to regulate and shift energy supply with the energy sources they now have, the difficult task is how do they do this with customer-based power systems; the customer has far too much independence for their comfort. Customers would need to become liable to the utility for failure problems or let the utility have operational control of the system performance and operation.

Now let’s look at the customer’s position. The customer doesn’t have a choice when shopping for a utility; moving to another location is the only option if you don’t like the utility in your area. This is often a source of discontent for the customer. Customers depend heavily on electrical power for almost every appliance in the home and business. Natural gas, propane and fuel oil for heat are the exceptions.
Electricity seems expensive because we use so much of it; in fact, it is pretty cheap. In order to generate all your own electrical energy on-site, the cost will be excessive. In order to meet the cost per kWh from the utility, the PV system cost needs to be amortized over a 25-year period. Most residential customers do not appreciate how difficult it is to provide constant electrical power and how reasonable the price actually is. Commercial customers are more aware of this yet they would still like to be more independent for the utility if it is possible.

An important factor to both residential and commercial PV system customers is the return on investment. The customer wants the highest price for the kWh generated from their PV energy and they feel justified because they are generating clean energy and contributing to the reduction of conventional fuel sources with known hazards to our environment. This actually makes sense when looking long range. If the utility can absorb some of the cost of integrating PV energy into the grid, the industry will continue to grow and reduce initial coasts and therefore operating cost. Eventually the cost of PV systems with smart energy storage will be cheaper than any other energy source. It is rational to expect a public utility or a customer owned utility to invest in solar for the future by offering premium rates for the solar kWh. The problem with this position is that the rate to the customer will need to decrease over time with greater solar penetration, otherwise the investment from the utility will not have a positive return and the cost of electricity will have to go up. This is a difficult point to make to customers; someone needs to educate the electrical customer on how this will work to their advantage. The salesman for the solar contractor is unlikely do it and the customer will be much less likely to trust that information coming from the utility itself.

Effective open communication between the solar customer, the solar contractor and the electric utility is essential. Avoid adversarial positions and look for positions that benefits each entity.

 

Kelly Provence
Solairgen School of Solar Technology

 

Correct Sizing of a PV Array

Residential Solar PV Ground Mount SystemThe question of optimum PV array size is the first question to be answered when designing the PV system. There are several factors that have to be considered to arrive at the best size. The customer budget, the available area for the array and the purpose of the PV array are always primary considerations. The budget is usually the most flexible since the system can be financed. The second may be difficult to get around if the location options are limited and restrictive. The third part is where most mistakes are made. There are generally two types of systems, (1) stand-alone and (2) utility grid interactive.

The stand-alone system must be designed to serve the electrical loads throughout the year. The PV array is usually sized to serve the loads in the month with the highest ratio of electrical load demand verses available solar energy. As long as the electrical load demand is known and the solar resource is known, the calculation is made for each month of the year (Avg. daily loads kWh ÷ Avg daily insolation ÷ Power conversion efficiency % = ratio) The ratio is the exact size of the PV array necessary to offset 100% of the energy consumed in that critical design month. The hard part is usually determining the kWh of electrical consumption.

The stand-alone system can be off-grid with generator backup or grid supported. If it is grid supported a portion of the house electrical loads are served by the stand-alone system. The PV array is sized for the stand-alone portion of the house.

The graph below show a typical PV system output capacity compared to the electrical consumption for each month of the year. The PV array is exaggerated in size to cover the worst ratio months of the year.

Graph 1

Grid interactive systems must consider how much power can be fed into the electrical system and remain compliant with the utility interconnection agreement and the best power offset value. The most common interconnection agreement is Net Metering for the billing cycle. It is typically set to offset up to 100% of consumption with solar PV generation during the monthly billing cycle. Energy generation in excess of 100% is usually compensated at avoided cost, about 1/3rd the rate of retail. The obvious objective here is to not generate more than is consumed for each month of the year. The challenge is to project generation and compare it to consumption throughout the year.

The months that usually control the PV array size are in the spring and fall. We consume less energy during these periods because of the reduced need for heating and cooling. Coincidentally, these are usually the best two periods for solar PV generation because of clear skies and lower temperatures, April and May are typically the best generation months.

The graph below shows the typical electrical usage for residential customers. The PV system that is designed to offset 60% of the annual electrical consumption is generating 100% of that consumption during the month of April.

Graph 2

A third type of system is a self-consumption type system that requires energy storage and is designed to connect to the grid but not sell into the grid. The PV array size usually follows the same rules as the interactive guideline above, but it can be more complicated and requires a smart control system with consumption and generation metering to keep everything in check.

It is OK to oversize a stand-alone system but with interactive systems keep an eye on the low-consumption vs. high generation months.

Kelly Provence
Solairgen
www.solairgen.com

706-867-0678
info@solairgen.com

Graphis of Excess Energy to the Grid

How Solar PV Can Become the Primary Electrical Energy Source

In order to have this discussion, it is necessary to look at electrical energy consumption patterns. Our energy sources have to match the timing of our consumption. The graphs below show the typical daily electrical energy consumption patterns for residential and commercial consumers.

Time of Day End of Hour

 

Overall peak energy consumption is from 2:00 PM to 6:00 PM. Residential peak consumption is from 4:00 PM to 10:00 PM. Peak solar PV production is typically from 9:00 AM to 3:00 PM. The majority of the solar PV energy is being produced during non-peak consumption hours. If the solar PV system is sized to provide base-loads only, this addresses part of the issue. However, it changes the load demand on the utility grid and makes it difficult to maintain stability of the grid voltage and frequency. The chart below shows the changes to the load demand when solar is added to the grid during the peak solar hours of the day.

2012 represents very little solar generation. Each year shows the actual added solar generation effect and projected solar generation effect on total load demand.

It becomes increasingly difficult and expensive for the utility to meet this type of demand load variation. One solution is to face the PV array toward the afternoon sun. This would help with overall consumption patterns but not for residential consumption patterns. It doesn’t address the issue of cloudy days with little or no solar PV generation. This brings in energy storage as the best solution. The energy storage capacity needs to be large enough to absorb the excess solar PV energy produced during peak solar hours.

Overgeneration risk

Energy storage is the only real solution for solar PV to become a primary electrical energy generation source (EEGS). There are several types of energy storage: Batteries are the fastest growing type of energy storage with Lithium-ion being the leader of that group; the conversion efficiency is pretty high (80% to 90%). Pumped water storage has been used by utilities for this purpose in some sectors of the electrical grid; the energy conversion efficiency is a little lower (70% to 80%). Other forms of energy storage such as fuel cells and capacitors may develop further in the near future but they are not competitors at this time.

Battery storage is the most versatile means of energy storage and it is crossing the barrier of cost effectiveness for shifting loads to a different time of day. To effectively compete with the other EEGS, solar PV with energy storage must have a levelized cost of energy (LCOE) that is lower than the other sources. To calculate the LCOE, divide the total cost of energy by the energy generated during the life-cycle of the EEGS. Twenty-five years is the typical life cycle used for PV systems. The cost of energy includes initial cost and all operating costs during the period of analysis. The kilowatt hour of generation during the period of analysis must be de-rated for non-operational hours and the warranted degradation of the PV output.

Examples:

Residential:

8kW PV system with energy storage:       Net Cost: $3.30/W = $26,400

8kW x 5 sun-hours x .85 x 365 days x 25 years x 90% = 279,225 kWh

$26,400 ÷ 279,225 = .094/kWh

Commercial:

500kW PV system with energy storage:  Net Cost: $2.60/W = $1,300,000

500kW x 5 sun-hours x .85 x 365 days x 25 years x 90% = 17,451,562 kWh

$1,300,000 ÷ 17,451,562 = .0745/kWh

Utility:

20MW PV system with energy storage:  Net Cost: $2.00/W = $40,000,000

20,000kW x 5 sun-hours x .85 x 365 days x 25 years x 90% = 698,062,500 kWh

$40,000,000 ÷ 698,062,500 = .0573/kWh

The above examples show LCOE rates that are competitive in some markets but not in all. The installed cost of solar PV is continuing to drop and the energy storage industry continues to improve and reduce costs. As these trends continue into the very near future, solar PV with energy storage will meet and beat the LOCE of most of its competitors in all markets.

Kelly Provence
Certified Master PV Trainer
CEO, Solairgen School of Solar Technology

The Importance of Optimum PV Array Size for Solar PV Systems

Residential Solar PV Ground Mount SystemThe question of optimum PV array size is the first question to be answered when designing the PV system. There are several factors that have to be considered to arrive at the best size. The customer budget, the available area for the array and the purpose of the PV array are always primary considerations. The budget is usually the most flexible since the system can be financed. The second may be difficult to get around if the location options are limited and restrictive. The third part is where most mistakes are made. There are generally two types of systems, (1) stand-alone and (2) utility grid interactive.

The stand-alone system must be designed to serve the electrical loads throughout the year. The PV array is usually sized to serve the loads in the month with the highest ratio of electrical load demand verses available solar energy. As long as the electrical load demand is known and the solar resource is known, the calculation is made for each month of the year (Avg. daily loads kWh ÷ Avg daily insolation ÷ Power conversion efficiency % = ratio) The ratio is the exact size of the PV array necessary to offset 100% of the energy consumed in that critical design month. The hard part is usually determining the kWh of electrical consumption.

The stand-alone system can be off-grid with generator backup or grid supported. If it is grid supported a portion of the house electrical loads are served by the stand-alone system. The PV array is sized for the stand-alone portion of the house.

The graph below show a typical PV system output capacity compared to the electrical consumption for each month of the year. The PV array is exaggerated in size to cover the worst ratio months of the year.

Graph 1

Grid interactive systems must consider how much power can be fed into the electrical system and remain compliant with the utility interconnection agreement and the best power offset value. The most common interconnection agreement is Net Metering for the billing cycle. It is typically set to offset up to 100% of consumption with solar PV generation during the monthly billing cycle. Energy generation in excess of 100% is usually compensated at avoided cost, about 1/3rd the rate of retail. The obvious objective here is to not generate more than is consumed for each month of the year. The challenge is to project generation and compare it to consumption throughout the year.

The months that usually control the PV array size are in the spring and fall. We consume less energy during these periods because of the reduced need for heating and cooling. Coincidentally, these are usually the best two periods for solar PV generation because of clear skies and lower temperatures, April and May are typically the best generation months.

The graph below shows the typical electrical usage for residential customers. The PV system that is designed to offset 60% of the annual electrical consumption is generating 100% of that consumption during the month of April.

Graph 2

A third type of system is a self-consumption type system that requires energy storage and is designed to connect to the grid but not sell into the grid. The PV array size usually follows the same rules as the interactive guideline above, but it can be more complicated and requires a smart control system with consumption and generation metering to keep everything in check.

It is OK to oversize a stand-alone system but with interactive systems keep an eye on the low-consumption vs. high generation months.

Kelly Provence
Solairgen
www.solairgen.com

706-867-0678
info@solairgen.com

Image of a Poor Solar PV Installation

How to Prevent a Substandard Solar PV Installation

No one wants a poor PV system installation, but it happens from time to time. The good news is it’s 100% preventable but you should first understand the causes of a bad installation, and then learn how to prevent it. We tell you how.

Problem #1: The installer is unskilled and unknowledgeable about the correct installation process, but how do you determine that?

Solution: Screen the installer. Ask for references and evidence of their experience such as pictures, invoices, permits and inspection reports.  Ask how much training they received, and where they received it. You can even ask to see their graduation certificates. Inquire about industry certifications (NABCEP) and whether they have a contractor’s license.

If they can’t or won’t provide any of the above information, don’t contract with them no matter what they promise you. A reputable installer will be eager to provide their credentials.

Problem #2: A skilled and experienced installer wants to install a brand-new product that is not fully understood or tested in the industry. It is not uncommon in this industry for changes in PV products to outpace the contractor’s full understanding of them. Don’t be the guinea pig.

Solution: Insist on tried-and-true system components unless it’s just an improvement over a product that has been around a while. It’s best to see how those brand new products hold up during beta testing. Find out by going to the internet and doing some independent research. Don’t be afraid to tell your installer what you learned and that you prefer another product.

Problem #3: The contract price is too low for the contractor to make a profit. Incorrect bidding is common when a contractor is inexperienced, but underbidding occurs occasionally even for experienced installers.

Solution: It is best to find out the going price for the installation prior to accepting a bid. If you don’t know the going price, get more than one bid and then compare. Most companies will give you a generic bid without a problem.

Some Advice: If the installer you select has underbid the installation, it may save you money in the long run to offer a fair, renegotiated price. Some contractors are very honorable and will do the same good job even if they lose money, but some will not and that may cost you more down the road. And remember, a deal too good to be true is usually exactly that, untrue.

In summary, the real responsibility is on you, the customer. Take a day or two to learn about the PV products, the installation process and who the good contractors are. There are many organizations out there to help you. Here are a few links to get you started: American Solar Energy Society, Solar Energy Industries Association, NABCEP, IREC, and The Solar Foundation.

Finding skilled, experienced solar PV installers isn’t difficult, and eliminates the frustrating and very expensive future problems of a bad, or failed, solar PV installation.

Kelly Provence
IREC Certified Master Trainer
Solairgen School of Solar Technology

Graphis of Excess Energy to the Grid

Alternative to PV System Net Energy Metering: Improving Grid Stability

What alternative to net energy metering (NEM) with PV systems will improve the grid stability and reduce consumer dependence on it? Self-consumption energy storage PV systems are the answer.

Solar PV installations continue to grow in the residential and commercial sectors. Integrated energy storage continues to grow along with the PV installations, and both of these are growing at a strong pace in the industry.

NEM can be calculated on a daily, monthly or annual basis; most NEM agreements are calculated monthly. Whether the consumer generated energy is used by the consumer or sent back into the grid, the energy consumption is reduced at the retail rate. The problem with this setup is that most of the energy goes back into the grid during the middle of the day (solar hours) when consumer energy demand is low; this does not improve grid stability, and can make it worse. The graph below shows the typical energy consumption vs. solar energy generation for a residential customer.

Graphic of Energy Out to Utility

PV systems with energy storage can change this with the batteries storing energy that would otherwise be sent into the grid.

Graphis of Excess Energy to the Grid

The stored and redistributed solar energy will improve grid stability in residential by reducing demand during peak usage times. If time of use metering (TOU) is in place, this setup will reduce energy consumption during afternoon and evening high rate periods. This increases financial savings to the PV system owner.

The following graph shows the typical U.S. grid load demand curves for all electrical energy users.

Total Demand

Residential electrical energy customers with interactive PV systems are supplying power during the time of day when residential load demand is not at its peak. PV systems with energy storage can operate as self-consumption systems and improve their return on investment. Grid stability is improved to the point where grid operators can see reduced operating cost as this type of PV system penetrates more of the NEM market.

This type of PV system can also provide the customer with critical load circuits that will operate during a grid outage. Everyone wins with these systems and NEM policies are no longer a factor with the customer’s financial rate of return.

Kelly Provence