(a) Consider an electric heating system connected to the main grid. Demarcate this system following Example 2.3.

Particular System (PS) An electric residential heating system connected to the main grid.

PS (components)

Structural components: indoor electrical wiring, heater casing and mounting structure, building envelope (walls/windows/roof) as the heat-retaining structure.

Operating components: heating element (e.g., electric radiator or floor heating), thermostat/temperature sensor, controller/switching unit, electrical protection devices (fuse, breaker, overheating protection).

Flow components: electricity from the grid as input; thermal energy delivered to indoor space as output; heat losses from the building to the outdoor environment as output.

Peculiar Function (PF) Convert electricity supplied by the main grid into usable heat in order to maintain indoor thermal comfort.

C1 — Conditions of production It is physically possible to convert electrical energy into heat (Joule heating), and to transfer this heat to indoor air and surfaces through the heater’s structure and installation.

C2 — Conditions of reproduction The system must be able to operate repeatedly: functioning heater and controls, safe wiring and protection, stable regulation through thermostat control, and routine maintenance to prevent failures or unsafe operation.

C3 — External conditions Reliable grid electricity supply, electricity price, and outdoor climate conditions (especially low outdoor temperatures increasing heat losses) directly affect the system’s ability to reproduce its operation. User behaviour (temperature setpoint and usage schedule) also shapes demand.

(b) Classify the system demarcated in (a) following the examples presented in Section 2.4.

Following Section 2.4 classification:

Human-made system: the system exists because it is designed, installed, and operated by humans.

Material system: it is composed of concrete physical components (heater, wiring, controls, and building structure).

Dynamic system: its state changes over time (temperature varies, heating power switches on/off, demand changes with weather and occupancy).

Open system: it exchanges energy with the environment—electricity enters the system boundary, heat is transferred indoors and dissipates to the outside through losses (and often air exchange through ventilation/infiltration).

(c) During winter months, demand grows as temperature decreases. Think about a heating system that can function without electricity from the grid. Demarcate this potential system and compare it with (a).Off-grid-capable option: biomass stove heating (wood/pellet stove)

Particular System (PS) A biomass stove-based residential heating system able to function without electricity from the main grid.

PS (components)

Structural components: stove body, heat-resistant materials, chimney/flue, optional thermal storage mass (e.g., masonry or stones).

Operating components: combustion chamber, air intake control (damper), fuel loading mechanism (manual), ash collection, safety arrangements (e.g., proper ventilation and monitoring devices as supporting elements).

Flow components: biomass fuel and oxygen as inputs; heat released into indoor space as output; combustion exhaust gases through the chimney as output.

Peculiar Function (PF) Convert chemical energy stored in biomass fuel into usable heat for indoor heating without relying on grid electricity.

C1 — Conditions of production Combustion makes it physically possible to transform chemical energy into thermal energy, and the stove structure enables transfer of this heat into the indoor environment.

C2 — Conditions of reproduction Recurring operation requires continuous fuel availability, controlled combustion and airflow, a functional chimney draft, and regular maintenance (ash removal and chimney inspection/cleaning) to sustain safe and stable heating.

C3 — External conditions Fuel access and storage conditions, local safety regulations, outdoor weather (affecting heat losses and chimney draft), and indoor air quality constraints (ventilation requirements) shape whether the system can reproduce its operation in practice.

Comparison with (a)

Both systems aim to maintain indoor thermal comfort, but their external dependencies differ.

In (a), winter temperature decrease raises heat losses, which increases electricity demand, and the system’s reproduction depends strongly on grid availability and electricity cost as external conditions.

In (c), the system replaces grid electricity with fuel-based heat production, improving autonomy during grid disturbances, but it requires stronger reproduction conditions related to fuel logistics, manual operation, ventilation, and safety maintenance.

Conclusion: The grid-connected electric heating system is highly convenient and controllable but externally dependent on the grid, while the off-grid biomass stove system increases independence at the cost of higher operational and safety requirements.

Based on the two households presented in the tutorial, electricity consumption shows a clear seasonal pattern over the year, and it is strongly related to the outdoor temperature in Lappeenranta. For both households, electricity use is generally highest during the winter period and lowest during the summer period, while spring and autumn act as transition seasons with intermediate demand. This pattern indicates a negative relationship between electricity consumption and outdoor temperature: when outdoor temperatures decrease, electricity consumption increases, and when temperatures rise, electricity consumption decreases.

The comparison between the two households also highlights different sensitivity to temperature changes. One household displays larger seasonal variation with pronounced winter peaks and lower summer baseline demand, suggesting that its electricity consumption is more dependent on temperature-driven needs (e.g., heating-related loads). The other household shows a more stable consumption profile with smaller fluctuations across the year, meaning its electricity use is less affected by outdoor temperature changes. Overall, the tutorial results suggest that colder weather leads to increased household electricity demand in Lappeenranta, mainly due to higher energy needs for maintaining indoor comfort during the heating season.

3) Photo-voltaic generation converts the sun's radiation into usable electricity. In this task, you will get the direct solar radiation with 1 minute time interval from the Radiation observations at FMI. Plot radiation profile of three different days so that one must be in March, other in July and the last in December (regardless of the year). What measuring station was used? Compare the solar radiation in those 3 days and provide information about the potential of solar generation in those days. You can also select the measuring station (but write it in the answer).

Hint: Code like in the tutorial notebook.

Answer：

1. Task description

In this task, I used FMI Radiation observations to obtain direct solar radiation with 1-minute time resolution and plotted the radiation profiles for three different days: 19 March 2025, 19 July 2025, and 19 December 2025. The measuring station used was Helsinki Kumpula. The code is written to (1) automatically identify the March/July/December files based on the Month column, (2) convert the time column into a plotting-friendly format, (3) plot all three daily profiles in one figure for direct comparison, and (4) compute basic indicators (peak radiation and daily total radiation) to support the discussion of PV generation potential.

2. Install dependency

3. Code

4.Comparison and PV potential

The plotted radiation profiles reveal strong seasonal differences. On 19 July 2025, direct solar radiation lasts for the longest part of the day and remains high for many hours, which leads to the largest daily total radiation and therefore the highest PV generation potential. On 19 March 2025, radiation is clearly present during daylight but for fewer hours than in July, resulting in a smaller daily total radiation and moderate PV potential. On 19 December 2025, direct solar radiation remains close to zero throughout the day, producing an extremely small daily total radiation and thus minimal PV generation potential. Overall, these three profiles demonstrate that solar PV potential in Finland is highly seasonal, mainly driven by daylight duration and solar elevation.