Introducing renewable energy into existing buildings, and what has to happen first

Renewed Efforts

Introducing renewable energy technology into existing buildings is a popular route to achieving savings. But its crucial to optimise current energy use first to avoid throwing good money after bad

by Glenn Massey

Saving energy and reducing CO2 emissions are top of the agenda for landlords, property managers and FMs right now. And current and pending legislation such as the Energy Performance of Buildings Directive (EPBD) and the Carbon Reduction Commitment (CRC) is stimulating change in the built environment.

In the quest to reduce energy it can be tempting to rush into quick fix solutions. Bolt-on renewable and low to zero carbon technologies, such as photovoltaic arrays, wind turbines and solar thermal, are often seen as the answer. ;These moves all have a part to play, but the first step should be to optimise energy consumption by removing its wasteful use. There is little to gain by generating energy from renewables only to waste it on inefficient building operation.

Improvements to energy use in existing office buildings fall broadly fall into three categories:

• Replacement of inefficient fixed building services and improvements to fabric.
• Changes to the way that energy is managed.
• Integration of renewable and low to zero carbon technologies.

Stage one should be to ensure that robust systems are in place for the management and measurement of energy.

Buyer beware!

Watch out for sales people touting the Òlatest energy saving marvelÓ. Instead, always look at the numbers and make sure the proposed solution is tested and that suitable guarantees are given. Always seek suitable professional advice before spending any money. All buildings have their own characteristics; make sure the solutions proposed are appropriate for the building. To do this you need to get to know your building better. The three ways to achieve this are:

1. Make the most of your energy performance certificates (EPCs): The EPC calculation produces important data that shows the energy attributable to items such as heating, cooling, fans, pumps and hot water, taking into account the fabric and construction properties of the building. FMs should request a breakdown of data from engineers undertaking the EPC. This information can be used to assess the building’s energy potential in comparison to its operational energy consumption.
2. Find out if the major energy used is gas (for heating) or electricity: Understanding this helps to establish where to focus initial attention. If electricity is the major energy source in a building it follows that the major gains are likely to come from electricity rather than gas.
3. Understand your energy baseline: Where are the peaks? Undertake analysis of the energy used outside normal working hours. Most buildings have electricity supply meters that provide half-hourly data. This is the data that the electricity supplier uses to prepare invoices. They are happy to make this data available to you.

Buildings often use energy at times when there are no occupants in the building. Taking remedial action involves low capital expenditure but yields good returns.

Management and monitoring

Armed with this information an energy management plan can be devised and quick wins identified to reduce energy use.

Which renewable technology? Renewable and low to zero carbon technologies, such as wind, photovoltaic, combined heat and power (CHP), combined cooling heat and power (CCHP) and solar thermal, must be considered on a building by building basis and should be integrated only when energy use has been reduced.

Renewables have a valid part to play in reducing consumption. Undertake feasibility studies to determine which renewables or low to zero carbon technologies are appropriate.

A feasibility study should include an assessment of expected energy yield; an assessment of the building’s electricity and heating profiles; planning implications; site space requirements; maintenance implications; and site infrastructure implications.

Financial incentives: Consider government incentives such as Enhanced Capital Allowances. These help to make the financial appraisal of projects more appealing. Remember once the capital cost has been displaced the energy is free.

But don’t forget to factor in maintenance costs. After, all you must consider the whole life costing of renewable technologies. Maintenance costs, replacement costs and contracts for the repairs should be established at the outset.

Finally, always measure energy use and the energy produced on site and don’t forget to report successes. Sharing this knowledge will assist in planning for the future.

A case in point

How would all these considerations work out in practice? One case in point saw consultant engineers called in to a a 4,500m2 multi-tenanted office building after the FM raised concerns regarding the electrical energy bills. Their brief was to propose a range of solutions.

After a review and benchmarking of annual energy consumption it was determined that the building was using around 50 per cent more energy (125 kWh/m2/yr) compared to the nearest Cibse benchmark for a typical office of this type (see figure below).

The 50 per cent extra consumption can be considered ‘waste energy’. Once this was quantified a review of the energy used outside normal working hours was undertaken using the electrical supplier’s half-hourly data. This uncovered issues with the air conditioning system which started working far too early: between 2.30am and 3.30am each weekday.

The savings achieved by rectifying air conditioning control issues are shown below.

• Weekly Energy Savings- 1,098 kWh
• Weekly Energy Cost Savings- £110 GBP
• Weekly C02 Savings- 604 kgC02
• Annual Energy Savings- 57,081 kWh
• Annual Energy Cost Savings- £5,708 GBP
• Annual C02 Savings- 31,395 kgC02
• Annual Energy Saving- per m2 12 kWh/m2/yr

The results

In the context of building energy performance the yearly saving represents a reduction of 12kWh/m2/yr. This shows how quick wins can reduce energy waste and why it should be considered before renewables and low to zero carbon technologies are applied.

Further investigations highlighted deficiencies with the tenants’ sub meters. These failed to meet the requirements of Ofgem or the European Measuring Instruments Directive (MID) and did not carry the ‘Type Approval’ Certificate necessary to comply with current legislation. A meter replacement plan was put in place. The new meters will provide accurate half hourly data from tenants’ areas and assist in the analysis of energy use.

Once energy management issues were addressed a feasibility study to install a small onsite wind turbine was undertaken. Using the Rayleigh distribution methodology, which estimates expected energy yield when average site wind speed, size and type of turbine are known, engineers modelled a 6kW vertical axis wind turbine. The expected annual energy yield for this site was 16,032kWh.

When comparing the expected energy yield from the wind turbine (16,032kWh) with the energy saved by the optimisation of the air conditioning plant (57,081kWh) it is clear that the energy generated by the wind turbine would be wasted by the over-running of the plant if this had not been corrected. The study illustrates the positive benefits of undertaking a simple energy evaluation.

Glenn Massey is an associate at Hoare Lea