Urban occupation

When large numbers of small PV systems are installed on buildings in urban areas and then left for untrained occupants to operate with no professional support, there are risks that poor performance may not be picked up. Donna Munro takes a look at the lessons learned from large projects installed in the past.

Solar PV systems are expected to have a long lifetime, successfully producing electricity at or close to their original output level for at least 20 years. While it will take a few years for the PV system to generate the amount of energy used in its construction, after this point is reached the system has a positive impact on climate change and fossil fuel consumption.

The majority of PV systems operate well for many years, but this is not always the case. A design that does not make it sufficiently easy for the occupants to check the system performance will allow even minor problems to persist, which may significantly reduce energy production. Some systems may be incorrectly installed and operate below expected performance for years before this is picked up. Others may develop minor problems which are not corrected, often because of the occupants’ lack of knowledge and limited access to advice.

Unfortunately, it is not immediately obvious whether or not a PV system is operating at its optimum performance. Such systems operate silently and without mechanical movement. If a grid-connected system has tripped out, power is still available from the grid. Without the use of test equipment, the only way to tell if the system is working is to look out for warning lights or keep an eye on metering or monitoring data. If the operators do not know how to interpret this data, problems may go undetected.

Risk factors

The projects which are at greatest risk of accumulating problems are those with fairly small PV systems, with occupants who have no particular motivation to keep an eye on things, and where there is no easily accessible person to contact regarding queries or problems. This situation contrasts with one where an individual decision to purchase and install a PV system has been made. In this case the occupants can be expected to have some understanding of the system, the quantity of electricity expected to be produced, the guarantees available and contact information for the supplier in the event of problems. Nonetheless, issues may still arise in later years if the house is sold on.

Groups of houses occupied by social housing tenants can also be very successful, but such developments do require some care and forethought. Factors shared by successful projects include: housing estates with a stable population, involved tenant representatives, system follow-up by someone from the housing association such as an energy officer or an external maintenance service, and provision of information about the PV system to the tenants. The housing association can also keep an eye on the condition of the PV systems, act as a central contact in case of queries or problems and organize maintenance and repairs. However, this kind of role fits more easily into some housing associations than others.

With buildings such as schools or care homes it is important to make sure someone at the building ‘takes ownership’ of the PV installation. For example at one care home there was a fault showing on the display panel because one of the inverters was down, however it was not noticed or reported for some time. An operator’s handbook was available, but personnel changes since the system was installed and no maintenance personnel residing on-site created a situation where no individual held responsibility for monitoring performance.

Other projects which report few problems are large systems operated by professional personnel. For example, the Nieuw Sloten project in the Netherlands where PV is installed on approximately 70 houses and apartments. This PV system is owned by the utility company Nuon, which sub-contracts the maintenance to a specialist organization. The householders own the property, but not the PV system. The electricity generated is used within the district, but is not linked directly to the house on which it is mounted and the systems are operated as a single 250 kWp unit by the utility. The arrangement was chosen in order to minimize the costs of inverters, installation and maintenance and is monitored online. To date, the system has been trouble free to operate.

However, projects where utilities are responsible for operating individual systems on houses have had more mixed results, as the case study (which follows this article) on the Nieuwland project in the Netherlands shows. Recent experiences from the Nieuwland project are an urgent warning that ensuring the successful long-term operation of multiple small PV systems in urban environments takes long-term commitment. Despite a worldwide reputation as a showcase for architectural integration of photovoltaics in the urban environment, there are now doubts about some resident’s willingness to keep their PV systems at Nieuwland. The original contracts for the PV systems were set for 10 years. This time period is nearly up and contracts will need to be renegotiated. Unfortunately, some residents have not been happy with the maintenance service received and communication over recent years. The end result may be that some of the systems have to be removed, damaging the architectural integrity of the area.

Of course, the story of Nieuwland is not just a simple one of erratic maintenance and lack of communication. It also reflects a change in political direction in the Netherlands, a loss of political commitment to photovoltaics, with no incentives for solar energy between 2003 and 2008, unstable government policies, the changing ownership of utilities and subsequent changes in policy and the effect that changes in ownership can have on an organization’s sense of ownership and commitment to a project.

Ensuring urban success

The project PV Up-scale has developed best practice guidance on how to ensure urban PV systems are designed, commissioned, handed over and maintained so that they are most likely to be kept in good operating order. This guidance is focused on those potentially difficult PV installations in groups of houses or where they are installed in buildings with no specific connection to renewable energy or electricity generation. The recommendations cover the design, commissioning and handover, and on-going maintenance phases of a PV system life cycle.

During the design stage the designers need to consider how the performance of the system will be checked. A visual display is needed so that occupants can see whether or not the system is operating correctly. Simple systems may just have an operating light and a fault light, while more complex displays also provide energy production data. Energy production data can tell you if the system is operating as it should, however this is only effective if you have some idea how much energy should be being produced under normal operating conditions.

A connection to a remote monitoring service may also be provided. Some systems have a simple warning light system on site and more comprehensive data collection and display system available elsewhere via a remote monitoring system. There are commercial services that provide remote monitoring, yield and performance checks, with the aim of reducing costs by optimizing energy yields and system maintenance. By making use of advanced information technologies and satellite solar radiation data, the user can be informed quickly of the PV system malfunctions. The correct solution will vary depending on the type of system and who has responsibility for operating it.

The completed systems should be handed over to the eventual occupants in full working order, commissioned and grid connected.

Before hand-over it is important to check correct operation and administrative set up including:

  • PV system output — ideally this should be compared to expected output.

  • Grid connection — Ensure the export tariff is agreed and contracts signed if required.

  • Ensure electrical commissioning has taken place together with grid connection approval.

  • Visual display — check this is working correctly and understood by the operator.

  • Monitoring system — check this is working correctly.

  • Responsibility for checking performance may need to be specifically allocated.

  • Arrange insurance.

Clear operating and maintenance instructions must be provided including:

  • Operation and maintenance leaflets in a sturdy format.

  • Information about expected power and yields.

  • A point of contact that can reliably answer any queries and organize maintenance.

At some new housing estates, developers have been keen to include PV to boost their green image but have not given sufficient thought to explaining the systems to the occupants. The new occupants may have no knowledge of PV before moving into their new house and no particular interest in the system so long as it works. Correct operation needs to be checked and commissioning done by the developer or their representatives. In addition, all the paperwork needs to be complete, especially any relating to grid connection. This can be very complicated and should not be left for private householders to complete under such circumstances.

One of the advantages of PV systems is that they are low maintenance and easy to operate. Unfortunately this is sometimes interpreted as meaning they need no one to keep an eye on them. They may be good, but nothing is perfect or lasts forever without some assistance. A maintenance plan is therefore required which includes consideration of:

  • Is there a centralized monitoring system or is it the responsibility of individual building occupants to keep an eye on system performance?

  • Which individual will be responsible for keeping an eye on the system? Do they understand how the visual display works?

  • Do they know how much energy they are expecting to be generated and how to check it?

  • Who can they contact in the event of problems or queries? Providing the telephone number of the standard utility helpdesk is not sufficient if the person answering the call is not going to be able to answer the query.

  • How to transfer information in the event of personnel changes/sale of the house.

One possibility for ensuring the successful long term operation and maintenance of PV systems is to use an EnergyService Company (EsCo). This solution is being considered for projects such as the PV demonstration programme on municipal buildings in Barcelona. At the moment, maintenance of energy installations in public buildings is done by the General Services departments at the district level. The existing work load of these services, together with the special characteristics of PV installations compared to conventional electrical ones, has led to problems with the maintenance of the PV systems which may prompt a change.

Investing in people

People have to have a reason or incentive to maintain their interest in the performance of anything they own. Without such drivers, inevitably such systems will eventually fall into disrepair. Thus, if the financial value of the electricity generated by the PV installation is low and there is no inconvenience suffered if the system is not working, the result is likely to be poor performance in the long term. Financial incentives linked to generation, such as enhanced feed-in tariffs, provide a significant motivator for occupants to monitor and maintain such installations.

In the long term, any system will only be maintained if someone is interested in it and this will be strengthened if the system is providing some economic benefit or if occupants are proud of the sustainability of the building. The increasing availability of feed-in tariffs for PV generation across Europe and sharp increases in the price of oil may improve the economic incentives for an owner to check performance occasionally and take action if problems are noticed.

However, it may still be the case that — until the background level of knowledge of PV in the general population and in organizations such as utilities increases — specific knowledgeable points of contact will be needed to get problems resolved. These points of contact may be found in EsCos, Housing Associations, from municipal energy officers, PV installers or utilities.

Donna Munro is a renewable energy consultant working with Halcrow Group Ltd.
e-mail: munro.donna@virgin.net

Detailed case studies for all the projects mentioned can be found on the PV UP-SCALE web site: www.pvupscale.org

Case study: Nieuwland 1 MW PV Project, Amersfoort, the Netherlands

The world’s first really large-scale urban PV project was completed in Nieuwland, Amersfoort, in the Netherlands in 1999. The project includes over 550 houses, an elementary school, a kindergarten and a sports complex. The total installed PV capacity integrated into facades and roofs is 1.35 MWp, or about 12,300m². More than 35,000 visitors have been to Nieuwland to see the attractive and varied PV architecture and many people and companies have learned major lessons from this unique project.

The main investor in the €8.6 million project was the energy company REMU, later merged into the larger ENECO. One reason that REMU started this project was a commitment to support the development of solar technology. At that time, the Dutch government required the energy companies to develop their own energy and environmental saving programs. REMU’s programme focused on solar energy.

The Nieuwland project is designed on the basis of one house – one system though the size of individual systems varies, between 0.8 kW – 4.4 kWp. Each house has its own inverter and a feed-in meter. The electricity generated by the solar systems is supplied into the public grid. To date, no serious problems have occurred with regard to the grid connection.

In order to investigate the effects of various forms of ownership and management, the solar systems were installed on various different types of houses including one family houses and apartment buildings. Some of the houses are privately owned while others are rented from a housing corporation. In addition, the PV solar energy system on the roof can be owned by ENECO or owned by the house owner. The tenants of the houses with a PV system on the roof get 20% of the generated solar electricity (based on calculation) for free. House owners who bought their PV solar roof paid 25% of the system costs and get all of the solar electricity generated.

The energy company is responsible for maintenance of the systems for a period of 10 years. After the summer of 2008, ENECO and the residents will make new arrangements for the next decade.


Monitoring campaigns have been carried out in some of the years since the project started. Furthermore, the monitoring systems have been upgraded over time so that each house is now provided with a measuring instrument (Eclipse) on which the tenants can track the performance of their solar system. The Eclipse units can be connected to a PC to supply data which can be used to produce long-term overviews of the system performance. Distance monitoring is also possible through a data logger and modem.

Technical monitoring carried out in 2005 showed that:

  • The majority of the systems, about 80%, perform well.

  • Some systems perform below expectations. These technical problems are related to shorter strings — due to the chimneys within the PV area, malfunctioning invertors and shadowing by the neighbouring walls.

  • Some recent problems had not been solved, often due to simple barriers such as the tenants not knowing who to call when they noticed a problem.

  • Some monitoring units were not working.

The results of the analysis of one area are shown in Figure 1 (opposite)

Maintenance performance

Initially an experimental Performance Guarantee & Maintenance System was set up to manage the maintenance programme for the installations. For the first two or three years this worked well, with a consultancy company responsible for monitoring the performance of all the PV houses. During these first years of operation, there were many problems with water leakage into the roofs and some inverters also malfunctioned. Nonetheless, all of the problems that occurred during this period were solved.

However, after some years this guarantee and maintenance system was discontinued and the maintenance system no longer ensures good performance of all the PV systems. Furthermore, the energy company REMU (now ENECO) remains responsible for most of the maintenance, but when REMU merged into ENECO the company became less involved in PV.

At the start, REMU had delegated part of the maintenance programme to small specialist organisations, but after two or three years more maintenance had to be done than was expected, increasing the costs of the maintenance contract. These demands came from both the roof integration systems, where there were a few problems, and from maintaining the performance of the PV systems. Roof leakages were solved quickly, but the electrical and other technical problems were ‘collected’ by ENECO which carried out maintenance activities only a few times per year in order to save on the cost of the specialist maintenance sub-contractor. Between 2003 and 2007 maintenance was done on a minimum level and the performance of several PV systems went down quite significantly as a result.

Occupant experiences

A recent survey determined that the occupants of the PV houses value the lower electricity costs, the higher value of the house, the architecturally attractive roofs, the contribution to green energy generation and the environmental savings. However, they remain concerned about the leakage problems at the beginning of the project associated with the roof integration methods. Other concerns include the long periods at the beginning of the project required for repairs related to connection and inverter problems and uncertainties regarding the costs and responsibilities in the long-term.

The architecture of the PV roofs also tends to restrict the possibility of modifying or enlarging the house afterwards, for example precluding the possibility of adding a dormer. Furthermore, on some roofs there is no clear border in ownership between neighbouring house and/or between the property owner and ENECO.

In addition, some monitoring units (Eclipse) are not working and the tenants are not sure if that also means that their system is not working. The occupants also say they did not get a handbook for Eclipse and could not ask ENECO about these issues since they had no known contact person at the company.

An earlier social monitoring questionnaire and analysis had found that the majority of the respondents (66%) felt that they had received sufficient information about the functioning of their PV systems. However, 68% of the respondents felt that they had received insufficient information regarding the costs of PV systems, especially the costs in the long term. Remarkably, 11% of the respondents were not even aware that their house is connected to a PV installation while the majority of the respondents did not know how much electricity their PV system produces and less than 10% had connected their Eclipse monitoring unit to a PC.

While most of the original tenants had a basic understanding of PV due to excellent communication by REMU and the municipality between1997 and 2000, follow-up owners were often not aware of existing contracts and not well informed about PV. Now, some 10 years after the opening of this impressive urban PV project, breakdowns or poor performance of the PV systems are often not even noticed, except for roof leakages.

In the coming year it is expected that ENECO will try to interest the occupants in a continuation of the project, and they are expected to offer to improve the maintenance and service programme. It is unclear if they will be successful.

Lessons learned

The major lessons for ENECO to learn from this project concern the ownership and maintenance of so many dispersed PV systems. This was much more difficult than initially expected. Though a final conclusion cannot be drawn here, it is apparent that a number of connected problems must be solved, as sub-optimal or unclear ownership and poor maintenance have caused major problems during the lifetime of the project.

The Nieuwland 1 MW PV project was a ‘first of its kind’ development: never before had a BIPV project been implemented at such a scale. From an architectural point of view, the project was a big success. In addition, there were no negative impacts on the quality of the grid.

However, the project also showed that a PV company is possibly not the best contractor to guarantee water tightness of a house roof in combination with an integrated PV solar roof. The after-care of the PV systems has been more time consuming than anticipated and it looks like the growing pains are not yet over.

ENECO has offered the inhabitants tools to check the performance of their PV system, either through a display in their homes (the ‘Eclipse’ data-logger) or through the ‘Sundial’ internet service which can keep track of the performance of their system but this has not resulted in any significant error reporting by inhabitants. This may be partly due to ‘lack of ownership’ and lack of responsibility – the property owners did not make the investment – and a lack of substantial financial repercussion in the absence of high feed-in tariffs. Even so, the main reasons reported were simple problems such as a lack of contact data or simply not being called back when residents tried to call and ask questions or report problems.

It is therefore poor communication after handover with the occupants of the PV houses, rather than technical issues, which appears to be at the root of the major problems being experienced in one of the most famous PV projects in the world.

Case Study prepared by Horisun: Jadranka Cace and Emil ter Horst.
e-mail: jadranka@rencom.nl and eth@horisun.nl respectively.


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